Background and aims <p>History of multiple substance use disorders (SUDs) or polysubstance use is highly prevalent, associated with worse treatment outcomes and higher mortality rates compared to single substance use. Although a few longitudinal studies have measured recovery progress over time, no metric explicitly quantifying recovery from polysubstance use is available. Here, we introduce the concept of <i>proportion of remission (PrR)</i> that provides a more granular and nuanced measure of recovery in individuals with polysubstance use and investigate its association with various Quality of Life (QoL) domains. We also report on individual SUD’s contribution to QoL.</p> Design <p>Cross-sectional study design.</p> Setting <p>Remote study.</p> Participants <p>2,406 participants with polysubstance use (polySUD; i.e., a history of two or more substance use disorders).</p> Measurements <p>Participants completed DSM-5 questionnaires regarding their lifetime and past 12-month substance use, Quality of Life measures, and demographics. Remission status was determined for each SUD based on meeting the DSM-5 criteria (excluding craving) in the past 12 months. Proportion of remission was quantified as the number of SUDs in 12-month remission divided by the total number of lifetime SUDs.</p> Results <p>PrR was significantly positively associated with environmental (B = 12.13, 95% CI: [9.68, 14.59], f = 0.2), physical (B = 10.75, 95% CI: [8.23, 13.26], f = 0.17), psychological (B = 7.73, 95% CI: [5.93, 9.52], f = 0.17), and social (B = 6.69, 95% CI: [3.45, 9.93], f = 0.08) QoL, after adjusting for covariates. Across SUDs, individuals not in remission exhibited significantly lower QoL compared to those in remission, with stimulants having the largest effect sizes (f = 0.39–0.42).</p> Conclusions <p>We propose a novel construct of polySUD recovery: proportion of remission. Our results indicate the potential of PrR to capture gradual improvements in quality of life and reflect recovery progress.</p>