We present new low-frequency radio continuum observations of the galaxies NGC 0628, NGC 3627, and NGC 7331, taken at 327 MHz with the Very Large Array.

We complemented our data set with sensitive archival observations at 1.4 GHz and we studied the variation of the radio spectral index within the disks of these spiral galaxies. We also compared the spectral index distribution and the IR distribution, using 70 $\mu$m Spitzer observations.

The comparison between radio spectral index images and the dust emission gives valuable information about the propagation of the Cosmic Ray Electrons.