The improvement of nasal air flow often requires, in addition to septoplasty, surgery of the turbinates. In order to broaden our knowledge of the influence of turbinate surgery on nasal function, the authors investigated nasal models with different lateral walls by visualisation of flow patterns and rhinoresistometry. Anterior turbinoplasty and turbinectomy reduce the nasal resistance to air flow, but the respiratory function of the nose deteriorates. As the result of these experiments, a trimming of hyperplastic turbinates must create a normal shape of lateral nasal wall, because the respiratory function is based on nearly regular narrow cavities.