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Objectives To assess the efficacy of smartphone apps for smoking cessation (SC) used alone or combined with traditional interventions, and to determine whether apps based on psychological-behavioural theories (PBT) increase abstinence more than traditional behavioural apps.Study design Systematic review and meta-analysis.Eligibility criteria We included randomised controlled trials of smartphone apps, used alone or combined with traditional interventions, for SC among current smokers aged ≥15 years who intended to quit. Comparisons included: no intervention, minimal SC support, traditional interventions and apps based on traditional behavioural interventions.Information sources Databases (PubMed, Embase, Web of Science, Cochrane Library, CNKI, VIP, Wanfang) were searched up to 15 August 2025.Risk-of-bias (RoB) assessment We assessed RoB using the Cochrane RoB Tool 2.0.Synthesis of results We used random effects meta-analysis to estimate pooled effects and corresponding 95% CIs for each outcome across all comparisons. The primary outcome was 6-month continuous abstinence. Secondary outcomes included 3-month continuous abstinence and 7-day point prevalence abstinence (PPA) at 1, 3 and 6 months. Certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.Results A total of 31 studies (12 802 participants) were included. Low-certainty evidence from four studies (1402 participants) suggests that smartphone apps used alone may improve 6-month continuous abstinence rate compared with no or minimal support (RR 2.85, 95% CI 1.61 to 5.05; I 2=0%). When combined with traditional interventions, smartphone apps may increase 6-month continuous abstinence compared with traditional interventions alone (RR 1.98, 95% CI 1.24 to 3.16; I2=85.7%; 4 studies, 2163 participants; low-certainty evidence). Sub-comparison analyses indicated that, based on low-certainty evidence from three studies (1502 participants), smartphone apps combined with pharmacotherapy may improve 6-month continuous abstinence compared with pharmacotherapy alone (RR 1.77, 95% CI 1.09 to 2.88; I2=86.0%). High-certainty evidence showed that PBT-based apps significantly increased 7-day PPA compared with traditional behavioural apps, both at 3 months (RR 1.69, 95% CI 1.42 to 2.00; I2=0%; 2 studies, 2565 participants) and at 6 months (RR 1.36, 95% CI 1.19 to 1.54; I2=0%; 4 studies, 3258 participants).Conclusions Smartphone apps may be effective for SC compared with no or minimal support. When combined with traditional interventions—especially pharmacotherapy—they may result in large increases in abstinence rates over traditional methods alone. PBT-based apps demonstrated potential for supporting SC. However, the overall evidence remains of low certainty due to limited sample sizes and methodological limitations. These findings are exploratory and necessitate confirmation through further high-quality trials with longer follow-up.PROSPERO registration number CRD42025640624.