AIMS AND OBJECTIVES: To investigate (a) How nursing care is organised on wards where nursing staff work different lengths of day shifts, and (b) How length of day shift affects the staffing of wards. BACKGROUND: Twelve-hour shifts have become increasingly common worldwide but there are concerns about impact on care quality and safety. Eight-hour shifts, and how day shift length affects how nurses organise their work, and staffing, have been little studied. DESIGN: Case study. METHODS: The setting was two older people's wards in an acute hospital in England. Nursing staff on one ward continued to work 12-hr day shifts; staff on the other ward worked 8 hr late and early day shifts, with an afternoon overlap, for 6 months. Qualitative interviews were conducted with 22 nursing staff. Semi-structured observations were conducted from 12-15.00 (5 × 3 hr episodes on each ward). Data analysis was conducted using the Framework approach. RESULTS: Theme 1: Organising nursing care and staff activities, (sub-themes: Care delivery across a 12 hr shift; Care delivery on early and late 8 hr shifts; Staff communication and documentation; Staff breaks; Teaching, supervision and staff development); Theme 2: Staffing wards with different length of day shift (sub-themes:: Adequacy of staffing and use of temporary staff; Recruitment and retention of staff after introducing 8 hr shifts). CONCLUSION: Nursing staff organised care on 8-hr shifts similarly to 12-hr shifts but then felt dissatisfied with their care delivery and handovers. Nursing staff on both wards approached care in a task-focused way. There were concerns that adopting an 8-hr shift pattern negatively affected recruitment and retention. RELEVANCE TO CLINICAL PRACTICE: Changing from 12 hr to 8 hr day shifts may affect nursing staff satisfaction with their care delivery and handovers, and have a negative effect on staffing wards.