To date there have been no published studies of cognitive functioning in polycystic ovary syndrome (PCOS). This large internet-based study compared neuropsychological functioning in right-handed women with (minimum n = 135) and without PCOS (minimum n = 322), stratified according to use of anti-androgen medication and level of depression. Women with PCOS are thought to have hyperandrogenism and hyperestrogenism which was hypothesized to differentially influence cognitive function across cognitive domains. Performance did not differ according to diagnosis on mental rotation and spatial location tasks. Hence, no evidence to support the view that women with PCOS display a more masculine cognitive profile due to hyperandrogenism. Despite presumed hyperestrogenism, women with PCOS demonstrated impaired performance in terms of speed and accuracy, on reaction time and word recognition tasks. These findings are intriguing given the welt-documented roles of estrogen and testosterone in cognitive function. Overall, these findings suggest that PCOS is not associated with masculinized cognitive functioning, and, although associated with impaired performance on tasks considered to demonstrate female-advantage, such impairments are subtle and are unlikely to affect daily functioning. (C) 2007 Elsevier Ltd. All rights reserved.