Osteochondroma is called a benign cartilage-forming tumor arising from an aberrant subperiosteal cartilage. Multiple osteochondromas syndrome (MOS) is an autosomal dominant disease, the basis for which is mutations in the EXT (EXT1 or EXT2) genes. Osteochondroma is one of the most common benign bone tumors. According to the WHO data, it is detectable in 35% of benign bone tumors and 8% of all surgically removed bone tumors. A total of 491 cases of bone tumors were analyzed in the children and adolescents diagnosed at the Department of Pathoanatomy, Russian Children’s Clinical Hospital, Moscow, in 2009 to 2014. All the patients with osteochondroma were divided into 2 groups: 1) sporadic cases (n=63) and 2) tumors included in MOS (n=33). Both groups showed a preponderance of boys (39 boys and 24 girls in Group 1 and 21 boys and 12 girls in Group 2). Clinical, radiological, and morphological criteria for the diagnosis and differential diagnosis of osteochondromas in children and adolescents are given.