Abstract The steam gasification of high density polyethylene in continuous mode has been carried out in a conical spouted bed reactor. The effect of temperature (in the 800–900 °C range) and steam/plastic mass ratio (between 0 and 2) on the distribution of products (gas and tar) and their composition has been studied. In order to reduce tar formation, two catalysts have been used in situ, namely, olivine and γ-Al 2 O 3 . The spouted bed reactor has an excellent performance between 850 and 900 °C, and an increase in the steam/plastic ratio from 1 to 2 only improves slightly both carbon conversion efficiency (to 93.6% with steam/plastic ratio = 2) and hydrogen concentration (61.6%). The use of olivine and γ-Al 2 O 3 instead of sand gives way to a moderate reduction in the tar formation , whose yield is 4.8% with olivine. The syngas obtained has a H 2 /CO ratio of 2.2, with a low tar content whose composition (monoaromatics, mainly benzene) augurs well for the use of the syngas in DME synthesis.