Gender differences in neuropsychological functioning of patients with psychiatric disorders have been studied extensively in the last years. The available studies provide conflicting results, which can be attributed to the complexity of variables influencing cognitive sex differences. In this article we review the literature about gender differences in cognitive functions in healthy men and women and discuss the relevance of hormones, socio-cultural factors, educational factors and training on the occurrence of these sex differences. Furthermore we summarize the results from functional MRI experiments, which is a useful tool for noninvasively localizing areas in the brain involved in specific cognitive functions.