OBJECTIVES: Clostridium difficile infection (CDI) can lead to several complications from mild diarrhoea to toxic megacolon. The objectives of this study were to: 1) evaluate standard Time trade-off (TTO) and chain TTO techniques for eliciting utility of CDI-related chronic and temporary health states; 2) compare those values with those from Healthcare Professional (HCP) EQ-5D valuation; 3) evaluate methods of calculating utilities for health states worse than death (WTD). METHODS: Ten health state vignettes were developed from literature with input from HCPs. Participants from the UK public were interviewed: 50 for the pilot and 100 for the main study. Each participant provided sociodemographic information, ranking of health states by preference and responses to a Computer-Assisted Personal Interview TTO protocol for all states considered. HCPs provided EQ-5D data. Methods to apprehend the impact of extreme negative utilities were appraised: truncation and monotonic transformation. RESULTS: Temporary health state utilities ranged from (mean and (/) median from non transformed method; mean and median (/) from monotonically transformed method): -2.70/0.7;0.39/0.6 for mild diarrhoea to -32.50/-1.1; -0.23/-0.5 for colectomy. Chronic health state ranged from:  -2.37/0.5; 0.35/0.5 for chronic diarrhoea to -7.98/0;-0.13/0 for chronic renal failure. Population valuations were more severe for most health states when compared with HCP values. CONCLUSIONS: While transformation has an important impact on results, nowadays there is no reliable measure of utilities for CDI-health states. The proportion of participants judging health states as WTD was unexpectedly high; questioning the suitability of face-to-face TTO interview in this disease area. The monotonic transformation was convenient but lacks theoretical grounding. Other methods like Lead Time trade-off could add value to similar research.