While ensuring adequate access to care is a central concern in countries with universal health care coverage, unmet health care needs remain prevalent. However, subjective unmet health care needs (SUN) can arise from features of a health care system (system reasons) or from health care users' choices or constraints (personal reasons). Furthermore, investigating the evolution of SUN within a health care system has rarely been carried out. We investigate whether health needs, predisposing factors and enabling factors differentially affect SUN for system reasons and SUN for personal reasons, and whether these influences are stable over time, using representative data from the Canadian Community Health Surveys from 2001 to 2014. While SUN slightly decreased overall during our period of observation, the share of SUN for system reasons increased. Some key determinants appear to consistently increase SUN reporting over all our observation periods, in particular being a woman, younger, in poorer health or not having a regular doctor. The distinction between personal and system reasons is important to better understand individual experiences. Notably, women report more SUN for system reasons and less for personal reasons, and reporting system reasons increases with age. Given this stability over time, our results may inform health policymakers on which subpopulations to target to ensure access to health care is universal.