Red peppers (Capsicum spp.) are one of the most widely consumed vegetables in Korea; thus, improving the beneficial properties of peppers may have important public health implications. Peppers contain various active phenolic compounds, including capsaicinoids; therefore, developing cultivars with high levels of these and other functional compounds is of major interest. We analyzed and compared the physiological activities and functional compounds on 15 cultivars of red peppers, including 5 commonly consumed cultivars that were collected from markets in Korea, and 10 important breeding cultivars that were registered with the National Agrobiodiversity Center (RDA, Korea). Comparisons of polyphenol content showed that polyphenol levels were higher in the green stages of the 10 registered peppers than in the same stage of ‘Noggwang Gochu’ peppers collected from the market. Based on ABTS (2,2'-azino-bis-3-ethylbenzo-thiazoline-6- sulfonic acid) radical scavenging activity, all stages of the 10 registered peppers had higher antioxidative activity than did the green and red stages of ‘Noggwang Gochu.’ Overall, ‘Hongsinho Gochu’ and ‘House Put Gochu’ had the highest antioxidant activity levels and the highest functional content among breeding cultivars. Among landraces, ‘Jeonbuk Wanju’ red peppers had both the highest functional ingredient levels and the highest antioxidant activity levels.