A laser system for selective treatment of acne comprising: at least two laser sources (10) having wavelength ranging from 1690 to 1750 nm which supply a first and a second laser beam respectively； a first multi-mode optical fibre (18) having a length equal to or greater than 5 m receiving said first laser beam； a second multi-mode optical fibre (18) having a length equal to or greater than 5 m receiving said second laser beam； an optical combiner (20) receiving said first and second optical fibre (18) and supplying a third laser beam to a third optical fibre (21)； said third optical fibre (21) having a length equal to or greater than 5 m； said third optical fibre (21) receives said third laser beam and supplies, at its output, a fourth laser beam； a fourth optical fibre (24) which receives said fourth laser beam； a handpiece (27) associated with said fourth optical fibre (24)； said fourth laser beam having a distribution intensity variance lower than or equal to 15% with respect to the mean rated value, a diameter greater than 2.5 mm, and a maximum available fluence greater than 30 J/cm2.
