The author dealt with planimetric measurement of anterior-posterior projection of the heart, great vessels and thorax. The measurement was made on skiagrams of 180 persons without clinically verified cardiovascular disease, being at the age of 20 to 79 years. The communication present absolute values as well as relative size of both components of heart-vessel shadow (cardiac-vascular silhouette) in relation to thorax. The author considers the cardiothoracic ratio as the best way to express size of the heart for indicating what part of thorax area in%is occupied by the heart shadow. There was not any significant difference in the area of this ratio between men and women. The measurement also made it clear that it is solely the vascular component of the heart-vessel shadow, which increases with age, whereas the heart-vessel shadow itself remains unchanged in persons at the age of 20 to 49 years. The results of the measurement made it possible to assume most frequent value of cardiothoracic ratio and its possible upper physiological limit.

        Key words: radiogram of heart – cardiothoracic ratio – planimetric measurement