In the present work, a detailed description of the potential energy surface of N-hydroxyurea (NHU), at level of isolated molecule, was obtained. Since NHU displays its biological activity in water solution, such analysis, performed on the free molecule, is useful to clarify the role of the isomers that are expected to be present in solution, as a preliminary step for further studies on the solvated system. A detailed search of the most suitable method and basis set to be applied to the calculation of the conformational energy surface of the free molecule has been carried out. The conformational energy surface of the molecule has been built as a function of three torsional angles at MP2/AUG-cc-pVDZ//HF/6-31G(d,p) level, requiring the calculation of 24,624 points of a reduced cubic grid.