Aqueous solubility and permeability through biomembranes are important parameters for drug bioavailability. Nanoparticles can be considered as a useful tool for improving properties of poorly soluble and/or permeable active ingredients. Hydrochlorothiazide (Class IV of BCS) was chosen as a model compound. Antisolvent precipitation – solvent evaporation and emulsion solvent evaporation methods were used as techniques for preparation of twelve samples containing hydrochlorothiazide nanoparticles. Water solutions of the surfactants sodium dodecyl sulfate and Tween 80 were used in mass concentrations of 1, 3 and 5%. Acetone and dichloromethane were used as solvents of model compound. The particle size of the prepared samples was measured by dynamic light scattering. The particle size ranged from 4.2 to 102.2 nm. Tween 80, that yielded nanoparticles <15 nm, was a preferable excipient to sodium dodecyl sulfate.