We use long-slit spectroscopy along the major axis of a sample of 23 nearby disk galaxies to study the kinematic properties of the ionized-gas component in their inner regions. For each galaxy, we derive the position-velocity diagram of the ionized gas from its emission lines. We discuss the variety of shapes observed in such position-velocity diagrams by comparing the gas velocity gradient, velocity dispersion and integrated flux measured in the inner (r =~ +/-1'') and outer regions (r =~ +/-4''). This kind of analysis allows the identification of galaxies which are good candidates to host a circumnuclear Keplerian gaseous disk rotating around a central mass concentration, and to follow up with Hubble Space Telescope observations. Based on observations carried out at European Southern Observatory (ESO N.58, A-0564), at the Multiple Mirror Telescope, which is a joint facility of the Smithsonian Institution and the University of Arizona, and at the Isaac Newton Telescope operated by the Isaac Newton group at the La Palma island at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.