There is no logical limit to the number of people who can attend a webinar. Practically speaking though, you can be limited by the webinar platform you choose or the package you buy. This is assuming that you can attract many interested registrants. When it comes to the webinar platform you choose, two options stand out for giving you space for very many attendees. WebinarJam can allow you up to 5,000 attendees. Cisco Webex Webcasting however takes things to a whole new level. It provides virtual events of up to 100,000 participants.