A series of WS2/Al2O3 catalysts containing a varied amount of phosphorus (0.0, 2.5 and 6.0 wt% P2O5), sulfided at two different temperatures (873 and 1073 K), were studied by means of high-resolution transmission electron microscopy (HRTEM). The stacking of(002) layers in the WS2-2H crystallites of the "rag" structure increases with the addition of phosphorus, whereas its length is kept almost constant. At high sulfidation temperatures phosphorus shows a stabilizing affect on the catalysts by retarding the stacking growth of WS2 crystallites. Additionally, an aluminum phosphate crystalline phase is identified in the phosphorus promoted catalysts.