I will briefly introduce and motivate the pre-big bang scenario and discuss its ability to reproduce recent data from experiments measuring the Cosmic Microwave Background anisotropies. The pre-big bang scenario is a string motivated scenario and it is traditionally belived to produce isocurvature perturbations, while the observed anisotropies rules out pure isocurvature perturbations and suggest a flat spectrum of adiabatic density perturbations. However the decay of the so-called curvaton can convert the isocurvature perturbations into adiabatic perturbations and make pre-big bang a possible cosmological scenario.