Child Behavior Checklist 6–18 The CBCL 6–18 [56] was assessed with a sample of ASD youth in two papers [ 51, 67 ]. Pandolfi, Magyar and Dill [51] found internal consistency was good with r = 0.92 for the aggressive behaviour scale, but I found no evidence concerning reliability. Structural validity for the complete measure was good and analysis supported the original two-factor structure of the CBCL 6–18 (internalizing and externalising factors). Tests of unidimensionality of scales did not reach the cut off for acceptable fit for aggressive behaviour ( RMSEA = 0.10, CFI = 0.95 ); however, convincing arguments were provided to allow for correlated disturbances in the model for two item pairs (destroys own things/destroys others things and disobedient at home/disobedient at school). This adjusted model showed an acceptable fit ( RMSEA<0.06, CFI>0.95 ). Criterion validity was assessed by Pandolfi, Magyar and Dill [51] by comparing ASD children with and without a co-occurring emoti