Background: Canada is the only developed country with universal healthcare but no universal prescription drug coverage. Prescription drug coverage in Canada is often described as a “patchwork” system; eligibility for coverage varies by province and influenced by circumstance. Subsets of the population are eligible for partial or full provincial coverage for their prescription medications through public and/or private coverage. Methods: The extent and factors associated with misreporting of drug insurance and cost-related non-adherence (CRNA) to prescribed medicines were investigated in three study populations: Ontario seniors 65 and over, Quebec seniors 65 and over, and Quebec adults 25-64 using pooled data from the 2015/2016 Canadian Community Health Survey (CCHS). The rationale for these study cohorts was that the vast majority had partial or full coverage for prescription medications from a public and/or private source. The factors associated with CRNA to prescribed medicines were also explored in these three subgroups. Results: There is a degree of misreporting of drug insurance among Ontario seniors (17%), Quebec seniors (18%) and Quebec adults (9%). Quebec adults who declared CRNA to prescribed drugs had twice the odds of misreporting prescription drug coverage (OR 2.1 95% CI 1.3-3.4). Lower-income earners among Ontario seniors (OR 1.8, 95% CI 1.3-2.6), Quebec seniors (OR 1.7 95% CI 1.2-2.6), and Quebec adults (OR 3.4, 95% CI 2.3-5.1) were more likely to misreport coverage. Quebec seniors were more likely to misreport if they had less than a secondary school education (OR 1.4, 95% CI 1.1-1.8). Ontario seniors who were immigrants were more likely to misreport coverage (OR 1.5, 95% CI 1.2-1.8), as were Quebec seniors who were immigrants (OR 2.2, 95% CI 1.4-3.5). Ontario seniors who had a flu shot in the past 12 months (OR 0.7, 95% CI 0.5-9.9) and Quebec adults who had visited a GP in the past 12 months (OR 0.6, 95% CI 0.45,0.77) were less likely to misreport coverage. CRNA to prescribed drugs was reported by Ontario seniors (3.3%), Quebec seniors (2.5%), and Quebec adults (5.3%). Low-income Ontario seniors (OR 2.9, 95% CI 1.5-5.7) and Quebec adults (2.5, 95% CI 1.6-3.8) were more likely to report CRNA to prescribed medicines. Quebec adults with chronic conditions (OR 1.7, 95% CI 1.2-2.4) and those in self-reported poor health (OR 2.4, 95% CI 1.3-4.4) were also more likely to report CRNA to prescribed drugs. Conclusions: There appears to be a socio-economic gradient in misreporting and CRNA among Ontario seniors, Quebec seniors, and Quebec adults. Given most of these subgroups will have coverage, we hypothesize a degree of measurement error among responses. More specifically, respondents who report CRNA to prescribed medicines may reflect measurement error. / Thesis / Master of Science (MSc) / Canada is a country that prides itself on universal healthcare yet lacks an important component - universal prescription drug coverage. Hence, it is often described as a “patchwork system” whereby Canadians must rely on a combination of public and private drugs plans depending upon circumstance. As a result, a proportion of Canadians lack prescription drug coverage and may be unable to afford prescription medications. This study aimed to investigate self-reported knowledge of prescription drug insurance in three populations: Ontario seniors 65 years and over, Quebec seniors 65 years and older, and Quebec adults 25-64 years old. The determinants of misreporting of drug insurance among these study populations was the primary objective of this analysis. The association between cost-related nonadherence (CRNA) to prescribed drugs and misreporting was a key variable in the analysis. Although only a small proportion of respondents reported CRNA to prescribed drugs, Quebec adults 25-64 were more likely to misreport drug coverage if they also reported CRNA. This study has provided some clarity on the factors that influence misreporting of drug insurance by Ontario seniors, Quebec seniors, and Quebec adults. Given health policy decisions are often guided by studies based on this data, researchers may consider a degree of misreporting in responses. Policy should aim to reduce misunderstandings about their drug coverage.