Background: To assess the correlation between the antipsychotics (AP) mean daily doses, hospital stay duration and CYP2D6, DRD2 polymorphisms in naturalistic study. Subjects and methods: CYP2D6 polymorphisms *3, *4, *5, *6, *1XN and DRD2/ANKK1 Taq1A polymorphisms were genotyped in a cohort of 226 Caucasian schizophrenic inpatients. AP daily doses, hospital stay duration and AP treatment duration were taken from medical records. To compare mean daily doses of AP among CYP2D6 PMs, EMs, UMs and DRD2/ANKK1 Taq1A carriers the actual AP doses were converted to chlorpromazine (CPZ) equivalents and DDD (defined daily dose). Results: Significant correlation (p=0.004) between CYP2D6 metabolic activity and AP mean daily doses was observed only among DRD2/ANKK1 Taq1A polymorphic allele carriers: 250.53 (95%CI: 154.90-346.17), 473.82 (95%CI: 426.99-520.64) 602.77 (95%CI: 469.65-735.88) CPZ equivalents in PMs, EMs and UMs, consequently. PMs with DRD2/ANKK1 Taq1A CT genotype received significantly lower doses of AP comparing to CC genotype (p=0.02). Mean hospital stay duration of PMs+UMs was significantly higher comparing to EMs (66.4 days (95% CI: 56.9-75.8) vs 50.2 days (95%CI: 45.5-54.7); p=0.047). Conclusions: In a cohort of schizophrenia inpatients CYP2D6 metabolic activity affects mean AP daily dose only in the presence of DRD2 Taq1A polymorphic allele. CYP2D6 metabolic activity correlates independently from DRD2 Taq1A polymorphism with hospital stay duration. Subpopulation of schizophrenia inpatients with altered CYP2D6 activity (PMs and UMs) carriers of Taq1A polymorphisms needs special attention of clinicians in aligning of AP treatment.