Lemmens first burst onto the snooker scene in his home country when at the age of 16 he reached the finals of the
Belgian Amateur Championship, a record that would not be beaten until 2010 by
Luca Brecel. Three years later in 1990 he won the Belgian Championship after defeating five-time champion Mario Lannoye 7–2 in the final, as a result Lemmens went on to represent Belgium in the
1990 World Amateur Championship where he reached the final eventually losing 11–8 to Irishman Stephen O'Connor. Following on from this success Lemmens turned professional in 1991, in a time when the tour was a largely open affair with over 700 players allowed to compete professionally. He had several years on the tour but ultimately only managed to achieve limited success with an appearance in the last 32 of the
1993 Welsh Open being his most successful result and never having climbed higher than 167th in the world rankings. By 1997, Lemmens had fallen further in the world rankings, and dropped off of the
main tour at the end of the
1996–97 snooker season. In 1996 he once again competed in the
world amateur championship reaching the semi-finals before losing to eventual winner and
future world champion Stuart Bingham. ==Death==