The different types of zeolites occurring in the hydromagmatic volcano called Montana Escachada or Montana Pelada (Southern Tenerife), have been studied. The instrumental techniques of study include X-ray diffraction, scanning electron microscopy, X-ray fluorescence and microprobe analysis. Phillipsite and analcime were detected in amounts inversely proportional from the basis (more phillipsite) to the top (more analcime) of the volcano. A selective enrichment of the phillipsite in potassium and of the analcime in sodium was also observed. The abundance and the genesis of these zeolites are related to the eruptive mechanism and the physico-chemical conditions of the zone. Their formation is, in high degree, irrespective of the composition of the parent magma