The present invention relates to an oral and/or buccal composition in the form of a thin film of a pharmaceutically active ingredient weakly soluble in water and gastro-intestinal tract fluids, comprising particles of said active ingredient dispersed in a film-forming polymer, at least 50% by weight of the total weight of the active ingredient having a particle size distribution such that at least 90% of said particles have a size below 1000 nm, preferably less than 800 nm, and even more preferably less than 600 nm, and to the method of preparing that composition and the use thereof.
