Diagnosis of syphilis in children is a challenging problem due to wide variety of clinical manifestations, their similarity to other infections and diseases, and lack of medical vigilance. Material and methods. We conducted a retrospective analysis of the clinical manifestations of clinical forms of syphilis in different age groups of children (0—3, 4—7, 8—14, and 15—17 years old) and adults based on the primary medical documentation (medical histories of 151 children and 109 adults aged 18—59 years). We studied the duration of the disease, polymorphism, prevalence, characteristics, localization of rash, changes in hair growth, reaction of the lymphatic system, and results of serological tests. Results. Clinical manifestations of syphilis in children depend on the age, which is most pronounced during the secondary period of syphilis and in young children under 7 years. In secondary syphilis, clinical process becomes more generalized with the age of patients, true polymorphism of eruptions occurs and their amount increases. Conclusion. Pediatric patients should be examined with allowance for age-related clinical features of clinical forms of syphilis. This approach will improve the quality and timeliness of diagnosis of syphilis infection in children.