OBJECTIVE: The objectives of this study were to measure diabetic patients' quality-of-life (QOL), utility, and willingness-to-pay (WTP), and to examine the interrelationship between these measures. METHODS: Diabetic patients =18 years old were randomly selected from 2 hospital endocrinology clinics. Patients were interviewed to measure utility values using a visual analogue scale (VAS) and standard gamble (SG), and measure WTP for pharmacist-provided education using contingent valuation. QOL was measured via self-administered questionnaire containing the 36-item Short-Form health survey (SF-36), Diabetes Quality of Life instrument (DQOL), and Health Utility Index (HUI). Relationships between scales of QOL instruments, utilities, and WTP were tested using Spearman's correlation coefficients and regression analysis, and differences by study variables were tested using t-tests and analysis of variance. RESULTS: Two-hundred eighty-three patients completed the interview and questionnaire. Mean health-utility was 0.72 from VAS, 0.83 from SG, 0.83 from HUI2 and 0.73 from HUI3. Mean scores for SF-36 physical component (PCS) and mental component (MCS) were 45.4 and 50.2, respectively, and mean score for total DQOL was 0.70. Patients' mean WTP was $32.65. Age and number of diabetic complications were significant factors for VAS. The PCS and MCS were both significantly positively correlated with total DQOL, HUI2, HUI3, and VAS (all p<0.0001), but not SG or WTP. VAS and total DQOL were significantly correlated with each other, SF-36 subscales, HUI2, HUI3, and SG (all p<0.05), except for WTP. WTP was neither significantly correlated with any utility values (VAS, SG, HUI2, and HUI3) nor any QOL measures (SF-36 and total DQOL), but correlations were in the expected directions. CONCLUSIONS: The DQOL demonstrated strong correlation with SF-36 and utility values measured using VAS, SG, and HUIs, but weak correlation with WTP. Further research is warranted to comprehend the underlying factors relating QOL, utility, and WTP.