He first arrived in Spain in 2002 as part of the Moroccan contingent for the World University Cross Country Championships, which was being held in Santiago de Compostela that year.

[3] He came fourth at the 2008 European Cross Country Championships at the end of the year, helping the Spanish men to the team title.

[10] At the 2010 European Cross Country Championships he was the first runner to break from the front, although he was caught by Serhiy Lebid and finished as the silver medallist.

[14] He carried the hopes of the host nation at the 2011 IAAF World Cross Country Championships in Punta Umbría and was the first European to finish, taking 16th place.

[16] He missed the track season due to injury and returned in November, coming seventh at the Cross de Atapuerca then second at the Soria race.

[20] Lamdassem returned to the Edinburgh Cross Country in 2012 and won the long race, beating European champion Yeshetela.

[23] Returning to shorter distances, he came second to Kenenisa Bekele at the Great Ireland Run and won the Cursa Bombers in April.

At the start of the 2013 cross country season he made the top two at the Great Edinburgh race and the European Clubs competition.