The data comprises of baseline characteristics of participants recruited to a Feasibility Randomised Control Trial (RCT) such as age, gender, education, ethnicity and smoking behaviour prior to starting the study. The trial study tested if an online smoking cessation intervention could be delivered within an existing online mental health service platform, for people who suffer from common mental health disorders such as anxiety and depression.  The follow up data was collected at 7 time points over the duration of the feasibility which was 6 months.  Responses recorded were to questions about any attempts to stop smoking, any periods of abstinence and any use of smoking medication.  Measures were also taken at multiple time points using PHQ_9 and GAD_7 to assess levels of anxiety and depression.  A set of questions at three months and six months asked about levels of satisfaction with the trial procedures, and the stop smoking intervention itself.