We present the results of a kinematical study of the H II regions in the central area of the giant irregular galaxy NGC 4449. A new method is defined to determine the sizes of the regions. We obtained the integrated parameters of the H II regions: radius, luminosity, radial velocity and velocity dispersion. We define the size and luminosity vs. velocity dispersion empirical correlations for the giant H II regions in the galaxy, and show that the correlations only hold for nebulae with surface brightness higher than 2×1035 erg s-1 pc-2 in H α and with a supersonic single line Gaussian profile. The exponent of the fits are consistent with virial mechanisms.