Stigma and discrimination of persons diagnosed with mental disorder is a common issue. In many European countries, research studies on the prevalence and implications of this problem are conducted in order to better understand how to overcome it. In Poland, there is a scarcity of such studies, what results in neglecting this issue by the policy makers. The objective of the study is to assess the prevalence of stigma and discrimination affecting the patients hospitalized in psychiatric day units and in-patient wards between 2016–2017 as well as to analyze the relationship between the stigma and the quality of life and social disability in persons with a mental disorder diagnosis of F20–F48 according to ICD-10, aged 18–65, in a day ward and an in-patient ward settings. The pilot study presents the data gathered from a preliminary sample of 20 patients of both genders diagnosed with the aforementioned mental disorders, equaling 10 per cent of the targeted total study sample. The quality of life is assessed with WHOQOL-Bref, WHO-5 questionnaire and Rosenberg self-esteem scale, while social disability is measured with the second version of the Groningen Social Disabilities Schedule. The assessment of the impact of stigma on the social disability of persons with mental disorders and their quality of life can be useful in the context of developing evidence-based interventions for these persons, while it could also provide the scientific data to support public information campaigns aiming at tackling the stigma against persons with mental disorders in Poland.