While the link between delay discounting and drug addiction has been well established, much less is known about probability discounting (PD) in the context of substance abuse. This study is the first to investigate how opioid-dependent individuals make risky decisions about gains and losses using the PD paradigm. Fifty-six opioid-dependent adults receiving opioid maintenance therapy and 55 controls performed two tasks that assessed PD of hypothetical monetary gains and losses, and completed the Barratt Impulsivity Scale (BIS-11). Patient participants exhibited greater PD for gains than did controls, suggesting that patients were more risk-averse when considering potential rewards. Patients also demonstrated greater PD for losses, indicating that patients made riskier decisions to avoid a loss compared to controls. BIS-11 scores were not significantly associated with either discounting parameter, and PD of gains and losses were not meaningfully correlated. The results provide initial evidence that individuals addicted to illicit substances discount probabilistic losses and gains differently than non-drug abusing cohorts, and in a way that maps onto drug taking behaviour. This pattern of discounting has implications for substance abuse treatments that target problematic risk taking.