Objective: This study determines the psychological problems and coping strategies of children and adolescents during the lockdown applied in the early period of COVID-19 pandemic in Turkey Material and Methods: The study includes the data of an online self-report questionnaire applied between 12-17th April 2020. The questionnaire consists data about family and peer relationships, online education, psychological responses, activities and newly acquired hobbies during the lockdown. Results: A total of 717 participants, 278 children (mean age 10.36±1.49 years) and 439 adolescents (15.49±1.72 years) participated in online survey. A statistically significant difference was found in the child and adolescent groups in terms of age (p <0.005). Although girls participated in the survey more in both groups, this rate was significantly higher in the adolescent group (p = 0.017). Adolescents significantly more communicated with their friends via social media (p = 0.000) than children, children had more attention problems in online education than adolescents (p = 0.000). Pandemic caused similar-moderate levels of anxiety in children and adolescents, symptoms such as difficulty falling asleep, reluctance and attention problems were significantly more in adolescents, headache, fatigue and weakness were higher in children. During the lockdown, children and adolescents engaged in activities and had new hobbies at a similar rate to reduce their anxiety or spending time at home (p = 0.260, p = 0.870). While the children mostly spent time with their family, adolescents spent more time with technology and social media. Conclusion: The results of this study based on self-report will provide important data on children and adolescents during the lockdown period. The ongoing COVID-19 pandemic will have long-term effects, and the data of this early study may lead new studies, also the results may assist in taking measures in the field of child and adolescent mental health.