Background: Strengthening primary care is key to Hong Kong's ongoing health system reform. Primary care remains unregulated, private sector dominated and financed mainly out-of-pocket. This study sought to examine the association between patients' socioeconomic status (SES), source of health payments and the quality of primary care they accessed to inform policy discussions. Methods: Data was collected from 1,994 respondents in a stratified random telephone survey with a 68% response rate, using the validated primary care assessment tool (PCAT). Education, household-income and type of housing were selected as indicators of SES. Multivariable ordinal logistic regression models were created to examine associations between indicators of SES and scores of quality. Results: Higher household-income was most significantly associated with better experiences of quality. Respondents with HK$ 15000-39999(USD1934-5158) and HK$ 40000(USD5159) and above were 47%(OR 1.47, 95% CI 1.10-1.96) and 2 times (OR 2.07, 95% CI 1.38-3.09) more likely to experience better quality than the lowest-income group respectively. Income group HK$ 40000(USD5159) and above was 84% more likely to have better utilization (OR 1.84, 95% CI(1.21-2.78), and 2 times more likely to receive better comprehensiveness (OR 1.90, 95% CI 1.26-2.87). Patients who used only private insurance were 80%(OR 1.80, 95% CI 1.20-2.68) more likely to experience better quality than those who paid out-of-pocket. Conclusions: Our results show that the quality of primary care experienced in HK tended to be higher for those who had higher income and private insurance, and were able to pay out-of-pocket for the care. This indicated that the inequality in primary care is likely to be related with the private dominated primary care system in Hong Kong. More public responsibility on primary health care should be sought for in HK and similar contexts to reduce the inequality in primary care.[Copyright of BMC Health Services Research