Purpose
This study aimed to validate the psychometric properties of the CRAFFT (Car, Relax, Alone, Forget, Family/Friends, Trouble) by using item response theory (IRT) and further examine gender differences in item-level responses.

Methods
This study used the 13th (2017) Korea Youth Risk Behavior Survey data conducted by the Korean Centers for Disease and Prevention and analyzed data of 8,568 students who reported drinking alcohol in the previous 30 days. IRT assumptions including unidimensionality, local independence, and monotonicity were tested. A one-factor two-parameter IRT model was fitted for item parameterization (M2 = 76.92, 20 df, p < .001, root mean square error of approximation = 0.02). Graphics for item characteristic curves and item and test information curves were provided. Differential item functioning (DIF) analysis was evaluated to measure item equivalence between boys and girls.

Results
Unidimensionality and local independence were satisfied, and the dominant factor eigenvalue and variance were 2.48 and 41.3% in boys and 2.08 and 34.7% in girls, respectively, and residual correlations in paired items were less than .2. The discrimination parameters were estimated as 1.32–3.59 for boys and 1.30–3.64 for girls. The severity parameters estimated verity as −0.23 to 1.67 for boys and −0.32 to 2.17 for girls. DIF was detected for four of six items, “Car,” “Relax,” “Forget,” and “Family/friends.” However, its impact on the total score was negligible.

Conclusion
The CRAFFT is a valid and reliable screening tool to identify alcohol use problems for both boys and girls, exhibiting good discrimination, good coverage of severity, and negligible DIF.