People with severe mental illness (SMIs) are more prone to physicalillnesses, increased mortality and cognitive impairments, all of whichnegatively influence their daily lives. Physical activity (PHYS)programmes have helped alleviate SMI. LIFEHOPE is an ongoing researchproject with the purpose of developing a sustainable lifestyleintervention for physical and mental health. PHYS/cognitive adaptationtraining (CAT) is a newly created lifestyle intervention that providesgroup education and is based on CAT. It provides individualized supportfor PHYS and dietary change in a natural nursing environment. The aim ofthis study was to obtain further knowledge for developing a sustainablelifestyle programme by exploring psychiatric clients' experiences withPHYS and lifestyle habits, which we did by interviewing a localreference group, community mental healthcare users and community mentalhealthcare workers. Then, we developed a lifestyle programme for peoplewith SMI using information obtained from these focus group interviews.Our results suggest that there is a need for support and education, aswell as active interventions, in carrying out PHYS and dietary changesamong people with SMIs, and the PHYS/CAT may be a useful strategy.