We present a case study of a patient who was hospitalized with the initial diagnosis of psychotic depression with predominant delusions of poverty. During his hospital stay despite antidepressant and antipsychotic treatment with 150 mg of sertraline and 20 mg of olanzapine per day, no symptomatic improvement was achieved. Besides, the psychotic features have risen to the fore along with inadequately vaguely expressed affective component. What drew attention was the coherence and permanence of delusional judgements, which, albeit variable in expression, always concerned one theme – the belief of an inevitable bankruptcy. The whole clinical picture, both with the objectifying interview defining the order of emerging symptoms, was suggestive and the verification of diagnosis was made. Persistent delusional disorder with delusions of poverty with subsequent mood disorder was diagnosed. The treatment with 275 mg of clozapine per day was started and we observed a slow gradual withdrawal of psychosis as well as a total normalization of the affective range. The case illustrates the importance of differential diagnosis of mental states in which psychotic features coexist with affective symptoms. It is helpful to determine the sequence of the symptoms development. It should be noted that although the ICD-10 classification distinguishes exclusively 7 subtypes of persistent delusional disorder, in the clinical practice we can encounter other thematic areas of psychosis. It brings substantial therapeutic and prognostic implications.