to assess the sleep characteristics of middle school children during the COVID-19 pandemic. Cross-sectional study of sleep characteristics of children - residents of radioactively contaminated areas of Zhytomyr and Rivne regions, who underwent a routine examination in June-July 2020, after their stay from March to June 2020 in conditions of home isolation due to quarantine restrictions during the COVID-19 pandemic. Ninety six students of comprehensive public schools, aged 10-16, took part in the study. Sleep characteristics were assessed using the Pittsburgh Sleep Quality Index (PSQI-U indicator), translated into Ukrainian. During the period of the introduction of restrictive measures due to the COVID-19 pandemic, certain disturbances of sleep characteristics were observed, the imprint of which was a moderately increased total PSQI-U indicator, which was (3.89 ± 3.20) points. It was established that 19.79 % of children had insufficient total sleep time, and 2.08 % had significant sleep deprivation. The quality of their sleep was described as «rather bad» by 32.29 %, and as «very bad» by 4.17 %; 35.42 % of children complained about sleep disturbances, 67.71 % of children had signs of daytime dysfunction, 18.75 % had symptoms of insomnia. In the logistic regression model, quite significant prognostic factors of insomnia were: female gender (OR = 2.487; 95 % CI: 1.407-4.397); subjective determination of the negative impact of the pandemic on health, regardless of whether the respondent had COVID-19 or not (OR = 1.166; 95 % CI: 1.112-1.222), as well as living in the city (OR = 1.183; 95 % CI: 1.065-315). The introduction of restrictive quarantine measures as a result of the COVID-19 pandemic led to a violation of the daily routine of schoolchildren, which modified the characteristics of sleep. In almost a third of the examined children, the duration and quality of night sleep was insufficient for the physiological restoration of the body's reserves. A late choice of the start of sleep and violations of his hygiene had a critical impact on these indicators.