Description: Objective To examine the process of case finding for depression in people with diabetes and coronary heart disease within the context of a pay-for-performance scheme. Design Ethnographic study drawing on observations of practice routines and consultations, debriefing interviews with staff and patients and review of patient records. Setting General practices in Leeds, UK. Participants 12 purposively sampled practices with a total of 119 staff; 63 consultation observations and 57 patient interviews. Main outcome measure Audio recorded consultations and interviews with patients and healthcare professionals along with observation field notes were thematically analysed. We assessed outcomes of case finding from patient records. Results Case finding exacerbated the discordance between patient and professional agendas, the latter already dominated by the tightly structured and time-limited nature of chronic illness reviews. Professional beliefs and abilities affected how case finding was undertaken; there was uncertainty about how to ask the questions, particularly among nursing staff. Professionals were often wary of opening an emotional ‘can of worms’. Subsequently, patient responses potentially suggesting emotional problems could be prematurely shut down by professionals. Patients did not understand why they were asked questions about depression. This sometimes led to defensive or even defiant answers to case finding. Follow-up of patients highlighted inconsistent systems and lines of communication for dealing with positive results on case finding. Conclusions Case finding does not fit naturally within consultations; both professional and patient reactions somewhat subverted the process recommended by national guidance. Quality improvement strategies will need to take account of our results in two ways. First, despite their apparent simplicity, the case finding questions are not consultation-friendly and acceptable alternative ways to raise the issue of depression need to be supported. Second, case finding needs to operate within structured pathways which can be accommodated within available systems and resources.