The aim of the present study was to investigate the impact of genetic polymorphisms of the dopaminergic and serotonergic system (i.e., DAT, COMT, and 5-HTT) on different verbal and visuospatial WM maintenance tasks in a mixed sample of healthy probands and patients with schizophrenia, bipolar disorder, and obsessive-compulsive disorder. This evidence concerns the gene SLC6A3 and schizophrenia.