Aim. To analyze collagen types ratio in skin and aponeurosis in order to predict postoperative ventral hernias. Material and methods. The trial included 141 patients for the period 2012—2015. Group I (n=65) of patients without ventral hernias was divided into subgroup AI (primary operation, n=41) and BI (re-operation, n=24). Group II consisted of 76 patients with ventral hernias. We performed histological examination of skin and aponeurosis to define the collagen structure of connective tissue. Results. There were significant differences between collagen type I/III ratio in skin (2.81±0.52 in group I vs. 1.13±0.48 in group II) and aponeurosis (2.69±0.41 vs. 1.09±0.21, respectively, p≤0.05). We revealed strong direct correlation (r=+0.92) between aponeurosis and skin specimens in one group. Collagen type I level was 73.81±2.74% in subgroup AI and 72.03±2.47% in subgroup BI. Collagen type I was predominant (p≤0.05). Conclusion. In patients with ventral hernias collagen type I/III ratio in skin is 2.54 times lower than in patients without hernias. Significant correlation of collagen types in skin and aponeurosis (r= +0.92) allows to predict the risk of postoperative ventral hernias on basis of skin fragment.