This paper considers, from the theoretical point of view, the problem of diagnosing and treatment of depressive disorders in people with intellectual disability (ID), relying primarily on the results of previous researches, which stress the etiological, symptomatic, diagnostic and therapeutic specifics when it comes to depression and its correlates in this population. The interest in mental health and psychopathology of people with ID intensified during the seventh decade of the previous century, when it became clear that some cognitive and behavioral symptoms are not, as hitherto thought, only a part or a consequence of the syndrome of intellectual disability, but a sign of ongoing mental disorder. So, the idea of ''dual diagnosis'' was born, and now it provides guidelines for the growing number of studies which theoretically and empirically review different issues of mental health problems in people with ID. Likewise, the observation of syndrome groups of genetic disorders resulting in intellectual disability has led to the narrowing of the circle of genetic syndromes that carry increased risk for the onset of depression and its correlates, such as: Down syndrome, Fragile X syndrome and Prader-Willi syndrome. Potential diagnostic problem in people with ID, when it comes to depression, may arise from ''diagnostic overshadowing'' of depression symptoms, which often remain hidden under abnormal behavior and adjustment disorders, especially in patients with severe forms of ID. As a possible way to overcome these problems some authors have proposed the concept of ''behavioral equivalents of depression'' or behavioral disorders that evidently can be associated with depression, such as social withdrawal, aggression, hostility, irritability, psychomotor agitation or retardation. Intensification of these forms of behavior may be a sign of developing depression, and in that sense, this view represents a useful starting point. When it comes to therapeutic approaches, there is a general tendency in favour of psycho pharmacotherapy in the treatment of depression, although there is a growing number of researches that prove the favourable effects of cognitivebehavioral and psychoanalytic psychotherapy.