Hyperprolactinaemia is a significant side effect of antipsychotic medications and may cause sexual dysfunction. The aim of our study was to assess the effect of switching from long-acting injectable (LAI) risperidone to paliperidone palmitate (PP) on sexual function and prolactin levels in patients with psychosis. We carried out a prospective observational study during a 3-month period that involved 11 patients with psychosis treated with risperidone-LAI who suffered from hyperprolactinaemia and who were then switched to PP. Two assessments were completed: the first one before the switch and the second one 3 months after the switch. These assessments measured sexual function using the Arizona Sexual Experience Scale and assessed prolactin levels. Our results showed a significant decrease in serum prolactin levels (P=0.041). We observed a four-fold reduction in clinically significant sexual dysfunction that is suggestive of benefit, although the sample size is too small to be sure. Our study suggests that prolactin levels seem to decrease after switching from risperidone-LAI to PP in patients with a psychotic disorder.