Objectives: (1) To identify any demographic characteristics, which predict medicines adherence by reporting Necessity-Concern Differential (NCD) and Self-Reported Health (SRH) scores among Hong Kong hospital outpatients. (ii) To investigate any association between SRH and NCD in this cultural group. Methods: A total of 709 outpatients completed a questionnaire consisting demographic information, SRH and Belief about Medicines Questionnaire. Findings were analysed statistically. Key findings: Descriptive statistics suggested that older participants (mean age > 64 years) tended to report low SRH, but high NCD compared to younger respondents (mean age < 53 years). Males were more likely to return high SRH and NCD scores than females (56.9 versus 42.2% and 74.8 versus 64.6%, respectively). Chi-squared tests demonstrated that socio-economic status was not significantly associated with SRH and NCD reporting (P > 0.05). Logistic regressions indicated gender and age groups (young-old and old-old) were significant predictors of SRH reporting (P < 0.001). Moreover, patients with high SRH were more likely to report high NCD than those with low SRH (P = 0.02; OR = 1.53; 95%CI 1.07–2.20). This indicates that regular administration of the SRH item followed by specific questioning could enhance early identification of potential medicine non-believers and, subsequently, non-adherent patients who may require urgent interventions or monitoring. Conclusions: Demographic characteristics and significant association between SRH and NCD reporting support our claim that SRH opens new opportunities for prompt identification of potentially non-adherent patients. However, further interviews to determine the cause(s) of non-adherence are necessary to validate such findings.