Objectives of this study were to assess (1) prevalence of worries and symptoms of distress, and (2) perceived change in symptoms of distress by sociodemographic factors and preexisting vulnerabilities, among young Danes under the first COVID-19 related lockdown. Data were derived from online surveys, collected 7th-18th of May 2020. The study population included 11,245 young people (15-20 years of age), of which 1807 had participated in The Danish National Youth Study 2019 (DNYS19). Descriptive statistics and linear regressions analyses, including robust standard errors, were performed. All analyses were based on cross-sectional data, except analyses of preexisting vulnerabilities among responders from DNYS19. Few young people were very worried to get infected with coronavirus. Females reported a higher frequency of symptoms of distress than males. Perceived change in symptoms of distress, did not vary systematically based on age, cohabitation, nor physical health conditions. Individuals working, perceived a lower increase in symptoms of distress, than those studying etc. Females with symptoms of anxiety pre-pandemic, mental health disorders, and in families with economic hardship had a marginal higher perceived increase in symptoms of distress, than females without these difficulties. The tendencies were similar but nonsignificant among males, and for symptoms of depression pre-pandemic. In conclusion, during the lockdown, young females reported a higher frequency of symptoms of distress than males, and individuals with symptoms of anxiety pre-pandemic, mental health disorders, and in families with economic hardship were more likely to perceive the lockdown to be associated with an increase in symptoms of distress, than individuals without these difficulties.