Zeolite LTL in the potassic form (K-LTL) was used as support of iron. The precursor was characterized by temperature programmed reduction (TPR) and Mossbauer spectroscopy (MS) at 298 and 15 K. The catalyst was obtained reducing the precursor with H-2 and its structural properties were studied by H-2 chemisorption, volumetric oxidation and MS under controlled conditions at 298 and 15 K. Measurements of activity and selectivity were carried out at I and 20 bar in the CO hydrogenation. Two different types of active sites were detected: Fe-0 inside the zeolite channels and carburized iron on its external surface. The solid showed a high activity and selectivity towards fight alkenes in comparison with other iron supported systems (Fe/SiO2, Fe/Al2O3 and Fe/C). This behavior can be attributed to the high percentage of metallic iron promoted by potassium ions, located inside the zeolite channels. The external carbide crystals generate hydrocarbons in the diesel oil range.