The X-ray binary Cygnus X-3 is one of the most enigmatic object of the Galaxy showing spectacular radio flares and is a possible source of high energy particles. It is also a key to understanding the evolution of X-ray binaries since it may represent an important link between the X-ray massive binaries and the short orbital systems with important implications regarding the formation of millisecond pulsars and low-mass X-ray binaries. We propose to use the ISO satellite to constrain the exact nature of the binary system which is not yet elucidated. The source is heavily absorbed in the optical and becomes visible only in the infrared. Our scientific goal is to obtain a detailed near infrared spectrum of the central source and to search for an extended source as the remnant of an expected heavy mass loss from the system. By measuring the (2.5-12microns) spectrum with ISOPHOT we will be able to determine if the companion is a low-mass star or a massive Wolf-Rayet star, two possibilities considered in different theoretical models. The infrared map provided by ISOCAM will trace the characteristics of the surrounding medium and reveal possible evidence of high energy particle interaction.