Clinical decision support systems (CDSS) are designed to improve decision-making by providing information or recommendations relevant to a specific patient at the point of care. This review summarizes and categorizes CDSS outcomes in primary and long-term care. Almost all studies reported process-related outcomes (e.g., alert rates/overrides), approximately two-thirds were randomized controlled trials, and only three of 32 were conducted in long-term care. More research should be conducted using randomized controlled trials instead of pre-post studies and in long-term care settings.