The use of an ordinary mode reflectometer has already proved to be a good means for determining the density profile of a plasma, but the fact that this mode reflects where its frequency equals the local plasma frequency restricts its use to the region of the density gradient. The extraordinary mode reflectometry investigated here permits the observation of the scrape‐off layer as well as the near‐axis region and in certain conditions also the high magnetic field side of the density profile. It is also shown that this mode requires a range of frequency sweep for measuring a given density profile smaller than the ordinary mode. On the Petula‐B tokamak, the density profile has been measured in 200 &mgr;s, its evolution when applying the lower hybrid current drive could be also followed. Since the measurement is particularly sensitive near the reflection point of the wave, it could be used to determine precisely the position of magnetic islands and the fluctuation amplitudes. In addition, the access and place occupied in the vacuum chamber being very small, this diagnostic should be compatible with reactor conditions.