Abstract. The goal of the present study was to test whether and how emotions influence arithmetic performance. Participants had to verify arithmetic problems. True problems were either easier or harder problems. False problems were parity-match or parity-mismatch problems. The odd/even status of proposed and correct answers was the same in parity-match problems (e.g., 19 × 7 = 131) and different in parity-mismatch problems (e.g., 17 × 9 = 152). Before each problem, participants saw a positive (e.g., smiling baby), negative (e.g., mutilations), or neutral pictures (e.g., neutral face) selected from International Affective Picture System (IAPS). They had to decide whether each picture includes a person or not before verifying each arithmetic problem. Results showed different effects of emotion on true- and false problem verification. Participants’ performance on true problems showed decreased problem-difficulty after processing negative pictures and increased difficulty effects after processing positive pictures. On false problems, we found smaller parity-violation effects after negative pictures (i.e., decreased performance on parity-mismatch problems), together with larger parity-violation effects after positive pictures (i.e., decreased performance on parity-match problems). These findings suggest that emotions influence arithmetic performance via which strategy is used and how each strategy is executed on each problem. They have important implications for understanding the role of emotions on arithmetic performance, and more generally on how emotions influence cognition.