Aim. This study is a part of a prospective schizophrenia research project run in Krakow. The general objective of the project is a long-time observation of people with schizophrenia, starting from the first episode through the years of living with the illness, the assessment of treatment results and predictors. The goal of this study was to investigate whether the level of DUP before the first admission may have a prognostic value in regard to the further course of the illness. Method. Four indicators of treatment results were observed: the number of relapses, the overall time of inpatient hospitalisations, the number of inpatient hospitalisations and the severity of psychopathological symptoms assessed in 3,7 and 12 years since the first hospitalisation. DUP was estimated during a clinical interview with a patient and his/her family at the index admission. The severity of symptoms was assessed with BPRS-SA, the UCLA version. Results. The increase of the number of relapses in follow-up assessments was more prominent in the group with longer DUP (p < 0.001). The decrease of the results of BPRS (symptom improvement) was more prominent in patients with short DUP. They had significantly lower results compared to patients with long DUP at each assessment except the index hospitalisation (p equaled respectively: 0.449; 0.002; 0.012; 0.034 and 0.014). The decrease of positive symptoms was larger in patients with short DUP significant in all except the 7-year follow-up (p equaled respectively: 0.230; <0.001, 0.011; 0.214; <0.001). Conclusions. 1) A relationship was found between the duration of untreated psychosis and the dynamics of general and positive symptoms and the number of relapses. 2) There was no significant relationship between the duration of untreated psychosis and the dynamics of negative symptoms, whereas the relationship between the time and number of re-hospitalisations was on the brink of statistical significance. 3) A replication of some and the lack of confirmation of other long-time results observed by other researchers prompts us to conclude that there still is a need for further studies concerning the duration of untreated psychosis