Abstract Background Similar to psychoactive substances, certain internet activities can produce highly rewarding sensations, leading to addictive use. Previous research reported associations between internet addiction (IA) and substance use. Our aim is to identify key differences between internet users with low and high IA risk in terms of which substances they consume (alcohol, tobacco, illicit drugs) and in terms of internet activities they engage in. Methods The National survey on the use of tobacco, alcohol and other drugs was conducted in 2018 in Slovenia on a nationally representative sample (age range: 15-64 years; 62.4% response rate). Among people who used internet at least once per week (N = 7,413), we distinguished between internet users with low IA risk (n = 6,929; 93.6%) and high IA risk (n = 484; 6.4%), based on latent profile analysis of responses on the Internet disorder scale (IDS-15). Results Higher IA scores were associated with lower age (r = - .310), but not with gender. Significantly more users in the high risk group were using internet to access social media (%L = 54.4; %H = 73.1), pornography (%L = 7.8; %H = 18.2), video content (%L = 42.7; %H = 61.0), and videogames (%L = 13.1; %H = 25.8), compared to the low risk group. Higher IA scores were associated with frequency (r = .040) and volume (r = .179) of drinking alcohol, while no associations were found with tobacco smoking measures. Lastly, smoking marihuana (%L = 6.3; %H = 12.7) and using any other illicit drugs (%L=2.2; %H = 5.6) in the past 12 months was significantly more common in the high risk group. Conclusions The present study underlines the addictive potential of four internet content categories (social media, pornography, video content and videogames). People who are sensitive to the rewarding potential of internet content may also be more prone to seeking rewarding sensations associated with consuming psychoactive substances, in particular alcohol, marijuana and illicit drugs, but not tobacco. Key messages • Using internet to access social media, videogames, video content and pornography is significantly more common among individuals with high risk for internet addiction. • High risk for internet addiction is associated with consuming alcohol, marijuana and illicit drugs, but not with tobacco use.