Abstract: Introduction: Loneliness is defined as an unpleasant emotional response to perceived isolation and it greatly diminishes quality of life. Loneliness may lead individuals to spend more leisure time with technology and increase their risk of addiction. Similarly, when individuals have an addiction problem they may feel more isolated and lonely. Methods: In the present systematic review and meta-analysis, which was pre-registered in PROSPERO (CRD42023390483), we quantify the degree of association between technology-related addictions and loneliness. We searched on three databases on March 2024 for references that compared the degree of loneliness in a group of individuals with addiction and without addiction. Means and standard deviations of loneliness, or, alternatively, odds ratios, were transformed into Cohen´s d for statistical pooling through a random effects model Results: After screening 2369 reports, we extracted data from 25 studies. The total number of individuals across studies was 37261. Participants were between 13 and 30 years of age (median 20). Thirteen studies were centred in internet addiction, four research pieces studied gaming and three problematic smartphone use. Coherently, the most frequently used scale to identify addiction was the Internet addiction scale (IAS) (Young, 1998). Loneliness was typically quantified using a variant of the University of California Loneliness Scale (UCLA-LS) (Russell, 1996). The pooled difference between those with and without addiction yielded a standardized effect (Cohen´s d) of 0.52 (95% CI 0.35-0.69). While heterogeneity was high, there was no indication of publication bias/small sample bias. Similar differences were found when limiting to specific groups of addictions. Moreover, meta-regressions did not show an effect of age, sex or scale. Individuals with addiction obtained 48.62 (43.44-53.8) points in the UCLA-LS on average, compared to 42.68 (36.74-48.62) in individuals without addiction (SMD 5.63, 95% CI=2.94-8.31). Conclusion: Our key analyses indicate that individuals with technology-related addictions had greater feelings of loneliness. The effect could be characterized as moderately sized. Acknowledgements Gonzalo Arrondo Arrondo is supported by the Ramón y Cajal grant RYC2020‐030744‐I funded by MCIN/AEI/ 10.13039/501100011033 and by “ESF Investing in your future”; and the 2022-2023 Institute for Culture and Society (ICS) challenge on "Youth, relationships and psychological well-being" of the University of Navarra. Ursula Paiva is supported by FUNCIVA, Proeduca and UNIR. Gemma Mestre-Bach was supported by the 2022–2023 Institute for Culture and Society (ICS) challenge on “Youth, relationships and psychological well-being” of the University of Navarra.