What is ICD-10 code F91.1?

F91.1 is the ICD-10-CM diagnosis code for Conduct disorder, childhood-onset type. A behavioral disorder that begins in childhood (typically before age 10) characterized by persistent rule-breaking, aggression, and violation of others' rights across multiple settings. F91.1 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. F91.1 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. F91.1 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. F91.1 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for F91.1?

F91.1 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards F91.1 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

What should coders know when reporting F91.1?

Verify onset before age 10 and document symptoms present in home, school, and/or community settings Distinguish from adolescent-onset type (F91.2) by confirming early childhood onset

F91.1 ICD-10 Code: Conduct disorder

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupF91.1Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Mental, Behavioral and Neurodevelopmental disorders (F01-F99) / Behavioral and emotional disorders with onset usually occurring in childhood and adolescence (F90-F98)

F91.1

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Conduct disorder, childhood-onset type

A behavioral disorder that begins in childhood (typically before age 10) characterized by persistent rule-breaking, aggression, and violation of others' rights across multiple settings.

Buddy Insight

Childhood-onset conduct disorder is defined by the presence of at least one conduct disorder symptom prior to age 10 years.

CMS-HCC V28

Not risk-adjusted for this model/period.

RAF 0

CMS-HCC V24

Not risk-adjusted for this model/period.

RAF 0

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Not risk-adjusted for this model/period.

RAF 0

RXHCC

Mapped

HCC 133

Personality Disorders, Anxiet...

RAF 0.0

Code Trumping

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Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

F91Conduct disorders

F91.1Conduct disorder, childhood-onset type

Inclusion Terms

Official

Unsocialized conduct disorder
Conduct disorder, solitary aggressive type
Unsocialized aggressive disorder

Excludes 2

Official

conduct problems associated with attention-deficit hyperactivity disorder (F90.-)
mood [affective] disorders (F30-F39)
pervasive developmental disorders (F84.-)
schizophrenia (F20.-)

Related Child Codes

Official

F91.0Conduct disorder confined to family context

F91.2Conduct disorder, adolescent-onset type

F91.3Oppositional defiant disorder

F91.8Other conduct disorders

F91.9Conduct disorder, unspecified

Includes

Official

ICD-10-CM does not list Includes notes for F91.1 in this effective period.

Excludes 1

Official

antisocial behavior (Z72.81-)
antisocial personality disorder (F60.2)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for F91.1 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for F91.1 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for F91.1 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Provider documentation of conduct disorder with at least one characteristic symptom present before age 10

Evidence of persistent pattern of behavior violating others' rights or major age-appropriate societal norms

Documentation of the age of onset of conduct symptoms

Assessment of severity (mild, moderate, severe) based on number and seriousness of conduct problems

MEAT Support

HCC Buddy guidance

Provider documentation of conduct disorder with at least one characteristic symptom present before age 10

Evidence of persistent pattern of behavior violating others' rights or major age-appropriate societal norms

Documentation of the age of onset of conduct symptoms

Assessment of severity (mild, moderate, severe) based on number and seriousness of conduct problems

Audit Caution

HCC Buddy guidance

Confusing childhood-onset with adolescent-onset type — the critical distinction is whether symptoms appeared before age 10

Using F91.9 (unspecified) when the onset history is available to determine the correct subtype

Diagnosing conduct disorder based on a single incident rather than a persistent behavioral pattern

Not reassessing and potentially updating the diagnosis as the child ages — some may progress to antisocial PD or resolve

Common Mistakes

HCC Buddy guidance

F91.2 — Conduct disorder, adolescent-onset type; adolescent-onset has no symptoms before age 10 and generally has a better prognosis

F91.0 — Conduct disorder confined to family context; family-confined type occurs only at home

F91.3 — Oppositional defiant disorder; ODD is less severe and does not involve violation of others' basic rights

F60.2 — Antisocial personality disorder; cannot be diagnosed before age 18, but childhood-onset CD is its precursor

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is F91.1 an HCC code?

No. F91.1 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.

HCC Category Mapping

RxHCCHCC 133, Personality Disorders, Anxiety, and Other Specified Mental Disorders

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

MEAT Criteria for F91.1

For F91.1to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed F91.1 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

F91.1 is the ICD-10-CM diagnosis code for conduct disorder, childhood-onset type. A behavioral disorder that begins in childhood (typically before age 10) characterized by persistent rule-breaking, aggression, and violation of others' rights across multiple settings. F91.1 sits in the ICD-10-CM chapter for mental, behavioral and neurodevelopmental disorders (f01-f99), within the section covering behavioral and emotional disorders with onset usually occurring in childhood and adolescence (f90-f98).

F91.1 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

F91.1 does not map to any HCC in V28 or V24 models. RxHCC maps to 133 (0.000). No RAF score impact. Accurate onset-type coding supports prognosis assessment and intervention planning. Coders reviewing F91.1 should check whether additional documentation would support a more specific child code in the same hierarchy that does map to a payment HCC, capturing the correct specificity is the highest-impact RAF improvement available within accurate coding.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for F91.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify onset before age 10 and document symptoms present in home, school, and/or community settings
•Distinguish from adolescent-onset type (F91.2) by confirming early childhood onset

Clinical Significance

Childhood-onset conduct disorder is defined by the presence of at least one conduct disorder symptom prior to age 10 years. This subtype carries a worse prognosis compared to adolescent-onset type, with higher rates of physical aggression, persistent antisocial behavior into adulthood, and development of antisocial personality disorder. Early identification enables intensive intervention that may alter the trajectory toward adult antisocial outcomes.

Documentation Requirements

✓Provider documentation of conduct disorder with at least one characteristic symptom present before age 10
✓Evidence of persistent pattern of behavior violating others' rights or major age-appropriate societal norms
✓Documentation of the age of onset of conduct symptoms
✓Assessment of severity (mild, moderate, severe) based on number and seriousness of conduct problems
✓Treatment plan including evidence-based interventions (multisystemic therapy, parent management training)

Commonly Confused Codes

•F91.2 — Conduct disorder, adolescent-onset type; adolescent-onset has no symptoms before age 10 and generally has a better prognosis
•F91.0 — Conduct disorder confined to family context; family-confined type occurs only at home
•F91.3 — Oppositional defiant disorder; ODD is less severe and does not involve violation of others' basic rights
•F60.2 — Antisocial personality disorder; cannot be diagnosed before age 18, but childhood-onset CD is its precursor