We present a study of the morphology, kinematics and star formation of a sample of 27 isolated spiral galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S4G), on the basis of Hα Fabry-Perot (FP) data from the GHαFaS instrument at the William Herschel Telescope (WHT) in La Palma, complemented with images at 3.6 micron from the Spitzer Space Telescope, and with images in the R-band and in Hα taken with the ACAM instrument mounted on the WHT. With the FP data we can investigate the gas kinematics in terms of velocity maps and position-velocity diagrams, keys to constrain the secular evolution processes. We can also analyse the morphology and compute the star formation rate (SFR) with the ancillary data.