The scholastic literature contains hundreds of references on subjects of exercise and Internet addiction. These two opposite addictions, in terms of physical-energy requirements and physical versus cognitive components, are examined. Commonalities and differences are explored in parallel. While both forms of addictions share common symptoms that meet the theoretically proposed characteristics of behavioural addiction, they are different in several ways: Exercise addiction is specific to a form or a collection of forms of physical activity(ies), but Internet addiction is unspecific (the activity could be sex, gambling, e-mail, shopping, video games and other). Exercise is an activity while the Internet is a medium on which different activities take place. The existence of these two addictive behaviours is also questioned while exploring co-morbidities accompanying these two problematic behaviours. It is suggested that both addictions may be manifestation of other behavioural problems rather then being a diagnosable psychiatric illness on their own. It is not surprising, then, that the DSM IV does not contain a classification for these problematic behaviours.