We have studied the kinematics of the ionized gas in the nearly face-on galaxy NGC 3938 by means of observations made with the Fabry-Perot interferometer TAURUS II at the William Herschel Telescope, using the H_α line. We have been able to produce high-resolution velocity and velocity-dispersion maps which allow us to make a detailed study of the kinematics of the ionized gas. In particular we have found that the vertical velocity dispersion is constant with galactocentric radius, as has already been found for the atomic and molecular gas in this galaxy. This suggests the existence of several heating mechanisms in the disc acting simultaneously to produce the observed behaviour.