The neuropsychological correlates of adolescent-onset schizophrenia have been investigated very little to date. We assessed intelligence, memory and executive function in 42 patients with adolescent-onset schizophrenia and 43 healthy control subjects. Cases showed impairments in most cognitive variables. Despite the overall similarity with the quantitative and qualitative performance characteristics of later-onset patients in the literature, their cognitive profile displayed a unique feature: modification of the usual pattern of thinking latencies in the Tower of London Task. After adjusting for potential confounders, no effect of illness duration, symptoms or medication dose on patient performance emerged. However, longer exposure to medication predicted a lower level of performance in aspects of attention, psychomotor processing speed and spatial working memory. Our data are not consistent with worse cognition or progression of neuropsychological impairment in adolescent-onset schizophrenia.