Born on April 16th 1982, Boris comes from a sporting family. His father Issa Diaw is a Senegalese lawyer and high-level athlete (high jump) ; his mother Elizabeth Riffiod was an international basketball player and captain of the French team (247 caps) and is considered to be one of the best pivots in the history of female basketball ; his brother Martin is a professional basketball player for the JSA Bordeaux. Boris spends his childhood in Mont-de-Marsan, where his mother plays in second division, then Pessac, when Elizabeth becomes a PE and sports sociology professor at the Bordeaux 3 University. The Talence and Pessac playgrounds become Boris and Martin’s world. After several clubs in Gironde, Boris joins the JSA Bordeaux to play at a good level.
After passing through the CERHN of Mont-de-Marsan, he joins the Toulouse CREPS. Boris gets noticed more and more on the court and plays with the France-under 16’s. Very fast he is scouted by Lucien Legrand to join INSEP. At this French basketball pole, in 1999, Boris plays alongside his future friends Tony Parker and Ronny Turiaf. After successfully graduating from high school, and winning the European championship with the French junior team led by Pierre Vincent, Boris starts his professional career at Pau.