This study examines major comorbidities in children with severe cerebral palsy and the feasibility of psychological tests for measuring abilities in a more impaired population. Eighty psychological evaluations of children with cerebral palsy aged 1.8 to 15.4 years (mean = 5.6) were analyzed. Major comorbid disorders were correlated with severity of motor disability. More than half of the cohort were diagnosed with severe cerebral palsy according to the Gross Motor Function Classification System. Multiple subtests were combined in order to assess the intellectual level. Normal intelligence was found in 22.5%, and 41.3% had moderate or severe intellectual impairment. Epilepsy occurred in 32.5% and attention-deficit hyperactivity disorder (ADHD) in 22.5%. Intellectual disability correlated with motor ability and with epilepsy. In a logistic regression model, epilepsy and motor ability score predicted 29.9% of IQ score variance. Intellectual impairment and epilepsy are common comorbidities. Subtests from different scales should be applied and interpreted with caution.