We present the development and validation of the Digital Addiction Scale for Teenagers (DAST), describing the pilot study (N = 40 students) and main study (N = 4493) with Estonian students aged 11-19, in spring 2020. Our aim was to create a scale suitable for psychoeducational assessment of teenagers' behaviour and feelings towards digital devices. We used the mixed research framework . Half of the study sample was collected before the coronavirus crisis (Sample I: 1972 students) and the rest during a distance-learning period (Sample II: 2521 students). We found that factor structure in both subsamples were similar. The DAST shows a negative relationship with emotional school engagement and life satisfaction and positive correlations with school burnout, learning difficulties and screen time. We discuss potential uses of the scale for assessing health-related digital competences.