Introduction: Hyperprolactinemia is a significant side effect of antipsychotic therapy. Risperidone, commonly used antipsychotics, is available in oral tablets and long-acting injections (LAI). This study aimed to investigate a potential difference in terms of prolactin levels among patients treated with these formulations of risperidone. Method: This was a naturalistic, retrospective, cross-sectional study. 91 patients with schizophrenia treated with risperidone in monotherapy were included into the study. 72 patients were treated with the oral form and 19 patients were treated with LAI form. All subjects had one measurement for prolactin level. Results: Our results showed that a mean dose of prolactin was significantly higher in the RIS- oral group and the difference was significant (p=0.019). There was no difference (p=0.59) in the percentage of patients with hyperprolactinemia in both study groups but more patients in the RIS-oral group had severe hyperprolactinemia and fewer patients in the RIS-oral group had mild hyperprolactinemia. Hyperprolactinemia was the main reason for discontinuation of treatment in the RIS-LAI group. Conclusions: According to the data from our study two forms of risperidone may differ in terms of impact on prolactin levels. Patients treated with LAI risperidone may have prolactin levels lower than on the oral form.