[en] Full text: Backscatter factors are also necessary for evaluating the entrance skin dose on patients that are submitted to radiographic exposure for establishing or verify the diagnostic reference levels for patient protection purpose. In this paper, backscatter factors were experimentally determined for the diagnostic X-ray qualities recommended by the International Electrotechnical Commission (IEC) for radiation qualities in radiation beams emerging from the x ray (RQR) and for radiation qualities based on a phantom made up of an aluminium added filter (RQA). Harshaw LiF-100H thermoluminescent dosemeters (TLD) were used for measurements after being calibrated against a Radcal Corporation 180 cm³ sensitive volume ionization chamber traceable to the National Metrology Laboratory. TL detectors were read out in a Harshaw 4500 Reader under a nitrogen gas flux with a standard annealing cycle. A 300 mm x 300 mm x 150 mm PMMA slab phantom was used for deep-dose measurements. The dosemeters were placed in the central axis of the X-ray beam at five different depths in the phantom (5, 10, 15, 25 and 35 mm) upstream the beam direction. The typical combined standard uncertainty of the backscatter factor value was 6%. The main sources of uncertainties were the calibration procedure, the TLD dosimetry and the use of deep-dose. Results showed that the backscattering factors varied from 1.2 to 1.7 for the quality RQR and 1.4 to 1.8 for the quality RQA that emphasizes the importance of a proper determination of them. It was possible to identify the contribution of each source of uncertainty in the BSF values. Results showed that BSF values varied significantly among the IEC RQR qualities. (author)