This paper investigates the effects of credit scores on consumer payment behavior, especially on debit and credit card use. Anecdotally, a negative relationship between debit card use and credit score has been reported; however, it is not clear whether that relationship is related to other factors, such as education or income, or whether it is a mere correlation. We use a new consumer survey dataset to examine whether this negative relationship holds after controlling for various consumer characteristics, including demographic and financial characteristics, consumers' perceptions toward payment methods, and card reward status. The results based on a single-year survey as well as on panel data suggest that there is a significant negative relationship between debit card use and credit score even after controlling for various characteristics. We supplement the analysis with evidence from Equifax data. The results indicate that an increase in consumers' cost of debit cards-in response to regulatory changes, for example-would have an adverse effect on low-credit-score consumers (typically those with lower incomes and less education). We then investigate what credit score implies. If credit score significantly influences consumer access to credit cards, credit limits, or the cost of credit cards, then the negative relationship likely results from supply-side constraints. If a lower credit score is associated with differences in underlying preferences, then the negative relationship is likely due to demand-side effects. Preliminary evidence strongly suggests that supply-side factors play an important role in the cost of credit and in access to credit.