Abstract Background Studies evaluating digital health technologies can be characterized by selective participation. Purpose We examined the reasons of (non)participation in a digital yoga study of patients with a long-term illness (80% heart failure) and the association with age and sex. Methods Reasons for exclusion of screened patients and for declining participation in invited patients were registered throughout the study. Differences in age and sex between patients that were eligible but declined to participate and patients included in the tele-yoga study were analysed using Student T-test and Fisher exact test. Results Of 3033 patients screened, 1401 patients (46%) were eligible for inclusion. Based on chart review and screening interviews, reasons for exclusion were not being in a stable condition to perform yoga (n=727, 24%), unable to complete questionnaires (n=176, 6%), not hospitalised in the last 3-36 months (n=66, 2%) and having a short life expectancy (n=42, 1%). Of 1401 eligible patients, 311 patients (n=22%) signed informed consent and were included. The main reasons for declining to participate were having no time for the intervention (n=294, 21%), not having the energy (n=150, 11%), and disliking or having doubts about yoga (n=147, 10%). Only 45 patients (3%) had doubts related to the technology as a reason not to participate (n=45, 3%). There were no age or sex differences between patients that were eligible, but declined to participate and those participating (67±13 vs. 66±12 years and 70% vs. 70% male, p=0.18 and p=0.52, respectively). Conclusions Results indicate that the tele-yoga study had a representative sample of patients with a long-term condition (80% heart failure) based on age and sex. As in many trials involving long-term illnesses, invited patients did not have time or energy to participate. One in ten where sceptical towards yoga but very few declined the digital format of the intervention.