Background and aims: Few preliminary studies have shown an impact of COVID-19 confinement on gambling habits. We aim to evaluate short-term effects of lockdown restrictions on gambling behaviors in Italy. Methods: Within the project Lost in Italy, a web-based cross-sectional study was conducted on a representative sample of 6,003 Italians aged 18-74 years, enrolled during April 27May 3 2020, and were asked to report gambling activity before the lockdown and at the time of interview. Results: The prevalence of participants reporting any gambling decreased from 16.3% before lockdown to 9.7% during lockdown. Traditional gambling decreased from 9.9 to 2.4% and online gambling from 9.9 to 8.0%. Among gamblers, median time of gambling grew from 4.5 to 5.1 h/ month. Among non-players before lockdown, 1.1% started playing. Among players before lockdown, 19.7% increased gambling activity. Multivariate analysis showed an increase in gambling activity in younger generations (p for trend 5 0.001), current smokers (odds ratio, OR 1.48), users of electronic cigarettes (OR 1.63), heated tobacco products (OR 1.82), cannabis (OR 5.16), psychotropic drugs (OR 3.93), and subjects having hazardous alcohol drinking (OR 1.93). Self-reported low quality of life (OR 1.97), low sleep quantity (OR 2.00), depressive symptoms (OR 3.06) and anxiety symptoms (OR 2.93) were significantly related to an increase in total gambling activity during lockdown. Discussion and conclusions: Although gambling substantially decreased during lockdown, time spent in gambling slightly increased. The strong relationship found between compromised mental health and addictive behaviors calls for urgent policies to prevent vulnerable populations from increasing and developing severe gambling addiction. Kulcsszavak: gambling, poly-addiction, mental health, COVID-19, lockdown, Italy