There is a connection between the chronic diseases and depression. A chronic disease can lead to a depression, or to an exacerbation of the existing depression. If the depression is caused by the chronic disease, that often leads to an aggravated course of the chronic disease. The chronic disease patients face an increased risk of depression incidence compared to the general population, but despite that, the existence of depression among those individuals is often overlooked. Namely; both the person suffering from a chronic disease and his social circle often think that the depression symptoms are “normal” and typical for a person suffering from a disease. Also, the depression symptoms can be hidden as symptoms of some other physical disease. The purpose of this scientific research paper is to determine the existence, incidence and level of depression among patients suffering from chronic diseases. Furthermore, the goal of this paper is to compare the incidence and level of depression among chronic patients with respondents who are not suffering from a chronic disease, and determine whether there are any significant differences. There is a statistically significant difference in frequency of depression sufferers in the group of chronic disease patients when compared to the control group. The chronic disease patients are more depressed than the control group. Statistically, the chronic disease patients group includes a significantly higher number of depressed individuals when compared to the control group. The recognition and treatment of depression in people suffering from a chronic disease might influence the outcome of the existing chronic disease in a sense that the patient’s compliance might be improved, or the depression symptoms intertwined with the chronic disease might be relieved or resolved, possibly leading to a quality of life improvement for the patient.