Participants in the intervention group will receive the DBT-ST by means of a free video-communication app. Over the next 14 weeks from the baseline, participants will receive two individual sessions (30-45 mins) and 12 group therapy sessions (120-minute)

Participants in the control group will receive a smoking cessation booklet published by the Hong Kong Council on Smoking and Health that provided information on the negative health consequences of smoking, reasons to quit, strategies for quitting, smoking cessation services available in Hong Kong, and a public Quitline number (usual care). Participants will also receive a monthly health education for three months that provides general health information and sharing sessions, which is one of the routine care for smokers during the first 3-4 months after they seek help for smoking problem (waiting period for further intervention).

Adaptive applications of DBT-ST for smokers with psychological distress

Participants who self-reported not smoking within the past seven days will be invited to attend a biochemical verification test of smoking abstinence

Symptoms of depression, anxiety and stress measured by the Chinese version of Depression, Anxiety, and Stress Scale-21

Self-reporting of complete abstinence for at least seven days prior to assessment

Client Satisfaction measured by the 8-item Client Satisfaction Questionnaire-8

Recruitment rate