Breakdown and extinction curves have been measured for RF capacitive low-pressure discharges in nitrogen and hydrogen at a frequency of 13.56 MHz and discharge gaps between 6 and 25 mm. In particular, the low-pressure, high-voltage region of the extinction curves is reported for the first time. The shape of the extinction curves was found to be similar to that of the breakdown curves. At sufficiently large gaps (L > 10 mm) the RF extinction voltage was found to be multi-valued in the low-pressure region, as is observed for the breakdown voltage. In this region, extinction can occur when the voltage is increased because the width of the two sheaths occupies the whole discharge space.