Adolescence is a biological, cognitive, psychosocial and emotional period. The development of cognition enables psychosocial development such as the development of one's own identity and self-direction according to one's own ideologies. In order for development to proceed properly, it is necessary to take care of mental health. From the city of Wuhan in China, at the end of 2019, an infectious disease started that affected the whole world. The World Health Organization called it COVID-19, and it appeared in the Republic of Croatia for the first time on February 25, 2020. By declaring a quarantine in the country and the world in order to prevent the spread of the infection, all educational institutions were closed, which directly affected adolescents by abolishing socialization, daily obligations and making new adaptations to online teaching and new ways of communicating with peers. Adolescents were under the magnifying glass of emotional disorders, behavioral and eating disorders, abuse of psychoactive substances, psychoses, suicides and self-harm. As the pandemic progressed, so did the rate of emotional disorders, especially anxiety and depression. Quarantine and social isolation have a negative impact on an individual's life. Disruption of mental health can cause shortterm or long-term consequences for an individual that we will only be visible in a few years when the affected adolescents will become people.