The present invention relates to a new solid pharmaceutical composition of didanosine comprising didanosine crystals with an average particle size comprised between 50 and 500 microns, coated by a layer of an enteric coating. The pharmaceutical composition of the invention can be prepared by means of a simple process, which comprises coating the didanosine crystals with an enteric layer. Said composition has a good stability of the active ingredient, as well as a suitable release in the conditions present in the upper part of the gastrointestinal tract. It also relates to the use of said composition for preparing solid dosage forms of didanosine for their oral administration. The invention also relates to tablets and to hard gelatin capsules containing said composition.