ABSTRACT: The Coronavirus-19 disease (COVID-19) pandemic has influenced the nutrition of individuals, including the diet followed, food availability, and food security. However, thus far, only a few studies have been published regarding the diet and activity of children and adolescents. The aim of the present study was to analyze the influence of the COVID-19 pandemic and remote education in this period on the diet and physical activity in a Polish population-based sample of primary school adolescents. In June 2020, the Diet and Activity of Youth during COVID-19 (DAY-19) Study was conducted on a population recruited based on stratified random sampling from all regions (schools sampled from counties, and counties from voivodeships). The sample consisted of a total of 1334 adolescents aged 10-16 years. The study assessed the diet and physical activity of the participants using a validated questionnaire which included questions about the period of remote education and the period before the COVID-19 pandemic. The participants were asked about the following: consumption of fruit, vegetables, soft drinks, water, French fries, and fast food; eating meals in front of the television; and the number of days they are physically active and the number of hours they spend watching television. The obtained data were analyzed by stratifying the respondents by the gender, age, size of the city and total COVID-19 morbidity in the voivodeship. It was observed that, during the pandemic and the resultant remote education, the proportion of respondents who declared the recommended intake of fruits and vegetables had increased compared to that before the pandemic-a higher proportion consumed at least three portions of fruit per day (19.0% before pandemic vs. 27.4% during pandemic; p < 0.0001), as well as three and four or more portions of vegetables per day (11.9% vs. 14.5% and 7.5% vs. 11.1%; p = 0.0004). At the same time, the proportion of respondents consuming at least three cups of water per day had increased (41.1% vs. 47.9%; p = 0.0020), whereas the proportion of respondents who never or rarely eat their meals in front of the television had decreased (35.6% vs. 28.9%; p < 0.0001), and the proportion watching television for more than 2 h a day had increased (78.3% vs. 88.4%; p < 0.0001). Based on the results, it may be concluded that, during the period of remote education due to the COVID-19 pandemic, the dietary behaviors of the studied population of Polish adolescents were more beneficial, which included a higher intake of fruit, vegetables, and water, compared to before the pandemic. In spite of the increasing screen time, including eating in front of the television, there was no reduction in the number of days the respondents were physically active.