Purpose of Review <p>This critical review examines the complex relationship between socioeconomic status (SES) and electronic cigarette (e-cigarette) use, addressing how SES influences patterns of e-cigarette use. It explores whether e-cigarettes serve as a harm reduction tool for disadvantaged populations or exacerbate existing tobacco-related disparities. The review also highlights key mediating mechanisms and policy implications of SES-related differences in e-cigarette use.</p> Recent Findings <p>Evidence points to divergent trends in e-cigarette use across SES groups. Initially, higher-SES adults who smoke were more likely to adopt e-cigarettes for smoking cessation, reflecting greater health awareness and access. However, recent data in several high-income countries show increasing uptake among lower-SES groups, driven by affordability, targeted marketing, and limited access to conventional smoking cessation support. Adolescents in disadvantaged settings may face higher exposure to pro-vaping cues across retail, peer networks, and social media, alongside weaker access to high-quality health information. Dual use (concurrent smoking and vaping) appears more prevalent in low-SES populations, raising concerns about sustained nicotine dependence and limited support for a complete switch from smoking to exclusive vaping. Structural factors such as income, education, occupation, and neighborhood/area-level deprivation, along with health literacy, shape vaping behaviors and help explain observed SES gaps. Regulatory measures such as flavour restrictions and taxation may have uneven effects across socioeconomic groups: they can help prevent youth uptake but may also create barriers for low-income adults who smoke and are trying to switch, with a risk of widening health inequalities.</p> Summary <p>The findings underline the dual role of e-cigarettes: while they may offer harm reduction opportunity for some people who smoke, their full benefits are not yet evenly distributed, with lower-SES groups facing barriers to complete smoking cessation. Equity-focused interventions, including tailored smoking cessation programs, accessible harm reduction pathways, improved health literacy, and balanced regulations, are critical to ensuring e-cigarettes reduce rather than reinforce socioeconomic disparities in smoking-related health outcomes. Future research should prioritise longitudinal and intersectional studies, particularly in low- and middle-income countries, to address existing gaps in understanding.</p>