There is limited evidence of genuine equal partnership where power is shared with young people with mental health difficulties throughout all research stages, particularly in data collection and analysis. To describe how our qualitative study, exploring young peoples' perceptions on the feasibility of using technology to detect mental health deterioration, was co-produced using principles of co-production, whilst reflecting on impact, challenges and recommendations. Young people with experience of mental health difficulties were appointed and then worked with researchers throughout all research stages. The study was evaluated against the five principles of co-production. Reflections from researchers and young people were collected throughout. Seven young people formed an initial Young People's Advisory Group (YPAG); three became co-researchers. Reflection was key throughout the process. Sharing power became easier and more evident as trust, confidence and mutual respect grew over time, particularly after a safe space was established. The safe space was crucial for open discussions, and our WhatsApp group enabled continual communication, support and shared decision-making. The resulting co-produced topic guide, coding framework, thematic map, papers and presentations demonstrated significant impact. To our knowledge, this is the first qualitative mental health study to be co-produced using the principles of co-production. Our rigorous assessment can be utilized as an informative document to help others to produce meaningful co-produced future research. Although co-production takes time, it makes significant impact to the research, researchers and co-researchers. Flexible funding for spontaneous suggestions from co-researchers and more time for interview training is recommended. © 2020 The Authors Health Expectations published by John Wiley & Sons Ltd.