Tourette Syndrome and Chronic tic disorders are characterized by the presence of tics. Different behavioral therapies have shown to be efficacious for treating tics in children and adolescents, but Exposure and Response Prevention (ERP) is a less researched method. However, ERP is a method often used in the clinical setting. Therefore, the present study evaluated the severity of tics over time from beginning of ERP to follow-up approximately one year after last training session. 116 patients treated with ERP face-To-face or ERP via web-based videoconferencing were included. Primary outcome measure was tic severity measured with the Danish version of the Yale Global Tic Severity Scale. The results showed that tic severity decreased during ERP and lasted in the follow-up period, with a statistically higher decrease in the group with patients who completed ERP as planned and the group that stopped earlier than planned because of reduction in tics, compared to those who dropped out due to lack of motivation (p<0.001). The study concludes that ERP seems to have an immediate and a long-Term effect on severity of tics, especially in those who complete the programme or those who discontinue earlier due to good results.