The aim of this study was to explore the anatomy and morphometry of the coronary sinus in hearts of adult humans, clarify position of the sinus to left atrium, left fibrous ring and adjacent arteries and describe topographic variants for adjacent anatomy of the coronary sinus in hearts of various types of coronary dominance. We studied 40 hearts weighing 200-420 g, obtained from patients who died from non-cardiac causes. We dissected 30 non-injected macroscopic specimens preserved into 4% PBS formalin to reveal and measure coronary sinus and neighboring coronary arteries. The rest 10 hearts we used for preparing histological slices from the points of the beginning of the sinus, in the middle, and near the “crux cordis”. We measured large and small diameters, circumference, wall thickness of the coronary sinus, as well as explored relative position of the coronary sinus, adjacent arteries, left atrium and left fibrous ring. The reference range of coronary sinus length was 33.76-48.4 mm. The median (Me) of the circumference of the coronary sinus increased from 13.87 mm at the beginning of the sinus to 23.99 mm at the “crux cordis”. In some specimens, the cross section of the sinus looked flattened in the anteroposterior direction; in others, it appeared to be flattened basoapically. We distinguished two anatomical patterns of the coronary sinus: subepicardial and intramyocardial. The first we proposed to term myocardialless or, simply, “naked”, and the second type we named muscularized. We proposed to divide the latter into partially and completely muscularized. Lack of adventitia between the myocardial sheet and tunica media of the coronary sinus allowed us to consider myocardial sleeves as an integral structure of the intramyocardial sinus wall. The wall thickness value of the coronary sinus at the point of origin, in the middle, and at the point of its turning anterosuperiorly toward the right atrium had no differences, but significantly depended on the myocardial cover and on the position of the coronary sinus in the left atrioventricular sulcus. The distance from the sinus to the posterior wall of the left atrium was 0.15-7.66 mm (Me 0.91 mm); the distance to the left fibrous ring was 2.9-13.7 mm (Me 7.9 mm). We found four variants of topographic and anatomical relations of the sinus and its adjacent arteries. Commonly, arteries were located below the coronary sinus. The ranges of variability of morphometric values of the coronary sinus and neighboring structures may be considered as reference values of the anatomy of the coronary sinus in the normal human adult heart.