With an increase in the legalization of recreational marijuana across the USA, advertising for marijuana products is more widespread, especially on the Internet where such practices pose a regulatory challenge. In this study, we examined the content of marijuana advertising on Weedmaps, a popular website that markets marijuana retailers online. A total of 146 recreational marijuana retailers in Colorado and Washington were examined on Weedmaps. We studied the age verification practices made in retailers’ own websites, the presence of health claims they made about marijuana on Weedmaps, and the characteristics of followers of Weedmaps on social media sites. Many retailers had no security measure to determine age (41 % in Colorado, 35 % in Washington). Approximately 61 % of retailers in Colorado and 44 % in Washington made health claims about the benefits of marijuana, including anxiety reduction, treatment of depression, insomnia, and pain/inflammation. Inferred demographic characteristics of followers of Weedmaps on Twitter and Instagram revealed that over 60 % were male and nearly 70 % or more were age 20-29 years old, yet some (15-18 %) were under the age of 20. Our findings indicate that marijuana retailers have a visible presence on the Internet. Potential customers might be enticed by retailers who tout health claims about marijuana use. It may also be appealing for a younger demographic to overlook age restrictions and engage with marijuana retailers via social media. As a whole, our findings can help to guide future policy making on the issue of marijuana-related advertising.