OBJECTIVE: To prove the connection between depression and cardiac disease by comparing depression in patients who had cardiac disease and patients from the same hospital that had some other (gastrointestinal) disease. DESIGN: The study was organised as an observational cross- study which was being held with control. The study consisted of two groups: a study group, whose participants had a positive cardiological history and a control group. The control group was presented by gastrointestinal patients who were not at risk of developing depression, i.e. they did not have a positive cardiological history. Primary resources of information that were used were obtained by applying the Hamilton Scale of Depression (HAM-D-17) on participants with cardiac and gastrointestinal disease. Previously composed tables were used. Based on the clinical interview, for each of the 17 questions asked, an appropriate answer was provided. SETTINGS: The Cardiology ward and the Gastrointestinal ward of Clinical Hospital Centre Split in Split, Croatia. PARTICIPANTS: The study included a total of 222 participants in the period of June, 2011. 111 of them were gathered on the Cardiology ward, the same was done for the remaining 111 patients on the Gastrointestinal ward. The criteria to participate in the control group was presence of a gastrointestinal disease, while the criteria for eliminating participation was the presence of a cardiac disease and malignity. The criteria to participate in the study group was presence of a cardiac disease, while the criteria for elimination was presence of a gastrointestinal disease and malignity. MAIN OUTCOME MEASURES: The total result for each participant is calculated by using the Hamilton Scale of Depression. The data was entered into an Excel table and processed statistically. By using the Mann-Whitney U Test a significant scale difference was expected between the patients on the Cardiology ward and the patients on the Gastrointestinal ward. RESULTS: While comparing the points that were obtained on the Hamilton Scale of depression between the patients treated on the Cardiology ward and the Gastrointestinal ward, a significant larger result is received in patients on the Cardiology ward (z=3,35; P=0,001). The median was 10 (4-30) for the cardiac patients, while for the gastrointestinal patients the median was 8 (2-26). There was also a significant growth in points on the Hamilton Scale of Depression as the age group is higher (χ2=27,8;P<0.001). CONCLUSION: This study proved the fact that the significant connection between depression and cardiac disease persists. The fact that when treating depression, we enhance the quality of life in such patients is generally known. This is why the conclusion of this study is important, meaning that screening depression in cardiac patients is extremely significant and recommended. Due to the fact that in this study elderly patients predominated, it is also important to pay attention and to treat other diseases (apart from cardiac disease) that are often presented in comorbidity with depression. They often mask and hide depression's symptoms and therefore complicate the whole treatment.