ENRecent research highlights the impact of prolonged pandemics and lockdown on the mental health of youngsters. The second wave of COVID-19 brought an increase in mental health problems among young people. Therefore, this study aims to analyze the main factors arising from intra individual, inter-individual, and environmental contexts that predict good psychological well-being in a group of adolescents after a second prolonged period of social restrictions and distance education. The study included 1483 school students from 11 to 19 years old. The survey assessed self-reported students’ psychological well-being (WHO-5 index), physical activity, sedentary behavior, school social capital, communication with peers and relationships with parents, existing emotional and behavioral problems. The results indicated that 58% of adolescents were of good psychological well-being in spring 2021, after half a year in lockdown. Almost 19% of adolescents had depression risk. The study revealed that during a period of prolonged isolation, male gender, better relationships between young people and their parents, the absence of serious emotional and behavioral problems, less sedentary behavior, and higher school social capital were found to be significant factors predicting adolescents’ psychological well-being. Lower physical activity is an important contributor to students’ poor well-being. Finally, the lack of face-to-face communication with peers was revealed as a specific factor in predicting adolescents with depression risk. Keywords: adolescents; psychological well-being; COVID-19; physical activity; social support. [From the publication]