BACKGROUNDPoor adherence to asthma and chronic obstructive pulmonary disease maintenance therapies impairs health outcomes. Proven and cost-effective programs to promote adherence and persistence are not yet in regular widespread use. Implementation costs are a potential barrier to uptake of such programs.OBJECTIVEWe undertook a systematic literature review and narrative synthesis of studies investigating the cost-effectiveness of treatment adherence-promoting programs or that determined their impact on health care budget directly or via health care resource use (HCRU).METHODSWe identified relevant publications using Medline and PreMEDLINE (PubMed), Embase (Embase.com, Elsevier), and EconLit for publications between January 2000 and July 2021. We also searched clinical trial databases and selected conference proceedings.RESULTSOf 1,910 potentially relevant articles, 26 met prespecified inclusion criteria and underwent data extraction. Eleven reported a direct assessment of adherence, 15 included economic evaluations, and 17 described HCRU. None included an analysis of biologic medication use. When they were studied, interventions were often found to be highly cost-effective, with dominant incremental cost-effectiveness ratios in some cases. Reductions in direct costs and HCRU (health care visits, hospital admissions, and/or the use of medications, including add-on/reliever treatment and antibiotics) were frequently reported. Reported use of maintenance treatments improved in some studies. Counseling and/or digitally informed programs were used in all cases in which favorable outcomes were observed.CONCLUSIONSAdherence-promoting interventions are mostly cost-effective and often result in reduced HCRU and associated costs. Multidisciplinary care involving one-to-one advice and digitally enhanced communications appear to offer the greatest benefit.