OBJECTIVES: Mental disorders constitute a major health problem with severe complications and a significant impact on quality of life.This study is the first comprehensive study on the direct and indirect costs of mental disorders (schizophrenia, bipolar affective disorder, depressive episode, recurrent depressive disorder and reaction to severe stress, and adjustment disorders) and associated complications in Poland. METHODS: In order to estimate the direct medical costs of mental disorders and their complications, including the costs of outpatient consultation, hospitalization, rehabilitation, and drugs, data from the National Health Fund were used with related etiological fraction calculus. Indirect costs embraced costs of lost productivity due to absenteeism and inability to work (handicap) caused by these diseaeses, and costs of lost productivity due to the premature mortality. They were calculated upon Social Insurance Institution and Central Statistic Office datasets using human capital method. RESULTS: Mental disorders is a cause of significant sickness absence and incapacity for work and therefore is associated with a growing productivity decline in Poland. The share of indirect costs consitute almost 70% of total costs and indirect costs amounted to EUR 2,9 billion. The highest direct costs are associated with treatment of mental disorders-related complications. CONCLUSIONS: The results of this study show that indirect costs can be higher than direct costs, and therefore cannot be ignored in health care decision-making processes. A major part of the total cost of analyzed mental disordes is indirect costs caused by productivity losses due to absenteeism and inability to work (55%). Most of these disorders can be successfully treated. The use of health care resources should be planned not only to cut direct costs of treatment but also to consider the social impact of the disease, through effective treatment to minimize indirect costs.