The purpose of this study was to evaluate positron emission tomography (PET) findings in patients diagnosed with infantile spasms and autism. This study includes 90 patients who were diagnosed with infantile spasms at the Department of Pediatric Neurology in the Istanbul University Medical Faculty between 1995 and 2007. Of the 90 patients, 15 patients who were diagnosed with autism using the Autism Behaviour Checklist and Childhood Autism Rating Scale and a control group of nine patients without autism but with infantile spasms underwent PET examination. Mean patient age (+/- standard error, SE) varied between 3 years and 16 years (7.8 +/- 4 years), while the mean follow-up time (+/- SE) varied between 2 years and 16 years (average: 7.1 +/- 4 years). Autism was present in 11 patients with symptomatic spasms and in four patients with cryptogenic spasms (p = 0.009). On the PET scans of the 15 patients with autism, 13 (86.7%) had significantly decreased metabolic activity in the temporal lobe (p < 0.001), nine (60%) had significantly decreased activity in the frontal lobe (p = 0.004), and seven (46.7%) had significantly decreased activity in the parietal lobe (p = 0.022). In our opinion, hypometabolism in the frontal and parietal lobes, in addition to that previously reported in the temporal lobe, plays a role in the development of autism in patients with infantile spasms. (C) 2012 Elsevier Ltd. All rights reserved.