To use virtual histology intravascular ultrasound (VH-IVUS) to assess the differences in tissue composition between chronic total occlusions (CTO) and non-occlusive lesions, especially in vivo. We compared 50 CTOs (49 patients) after guidewire crossing with 41 non-occlusive lesions (41 patients, 25 with unstable angina and 16 with stable angina). Overall, the percentage of necrotic core in the CTO segments was similar to non-occlusive lesions (35.6 vs. 38.7 %, p = 0.18 at the maximum necrotic core site; 24.2 vs. 23.7 %, p = 0.8 in mean analysis over the entire segment length). However, the percentage of dense calcium in CTO segments was less than in non-occlusive lesions (10.6 vs. 14.8 %, p = 0.025 at the maximum necrotic core site; 7.6 vs. 11.4 %, p = 0.036 in mean analysis over the entire segment length). Finally, the necrotic core/dense calcium ratio tended to be larger in the CTO segment than in non-occlusive lesions (2.94 vs. 2.35, p = 0.082 at the maximum necrotic core site; 3.05 vs. 2.03, p = 0.005 in mean analysis over the entire segment length). Overall, 42 (84 %) CTOs contained a fibroatheroma compared to 40 (97 %) of non-occulsive stenoses. The percentage of necrotic core in CTOs with a fibroathroma (39.0 %) was less than non-occlusive stenoses with a VH-thin cap fibroathroma (44.4 %, p = 0.017) and greater than non-occlusive stenoses with a VH-thick cap fibroathroma (33.5 %, p = 0.022) at maximum necrotic core site. These findings suggest that the morphological characteristics of most CTOs were similar as compared with non-CTO lesions and CTOs evolved from fibroatheromas.