BACKGROUND The COVID-19 pandemic affected drinking behaviors among adolescents. This remote questionnaire-based study aimed to compare alcohol use in 1030 final-year high school students in Split-Dalmatia County (SDC), Croatia before and during the national lockdown due to the COVID-19 pandemic. MATERIAL AND METHODS An online self-reported questionnaire survey was conducted among 1030 final-year high school students (57.96% female; mean age 17.71 years, SD=0.66) in SDC. The data were collected from June 6 to July 20, 2020 and from October 12 to December 28, 2020. Differences in drinking habits between groups were detected with the chi-squared (χ²) test and before and during the COVID-19 lockdown using the Z test. RESULTS Before the lockdown, 84.66% of students were consuming alcohol, most frequently with friends (78.64%) and "to feel better" (29.51%), while during the lockdown, 44.76% of them were drinking, most frequently with friends (34.37%) and due to boredom (17.48%). Drinking alone (P=0.005) and with family members (P=0.003) significantly increased during the lockdown. No difference in drinking between girls and boys was found before the lockdown, but boys were drinking more during the lockdown (P<0.001). There was no difference in drinking prevalence in different schools before the lockdown, but during the lockdown, more students from vocational schools were drinking (P<0.001) and with higher frequency (P=0.002). Among 53.98% of students during the lockdown, a reduction in frequency of drinking was found (P<0.001), most significantly on islands (P=0.05). CONCLUSIONS During the lockdown due to the COVID-19 pandemic, alcohol consumption by final-year high school students in SDC significantly decreased, particularly in girls and in gymnasium/private school students.