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We describe the stratigraphy and geochemistry of tephras and lavas related with 5 cinder cones in a north-south alignment on the southern flank of Poás volcano. The local geologic basement is composed mainly by lava flows, with the northwest dominated by the Achiote basaltic-andesites and the rest of the area by Poasito andesites, this last cogenetic with the cinder cones. All of these units are generally covered by a thin layer of the upper section of the Poás Lapilli Tuff. Field evidence suggests that the cinder cones were not contemporaneous but represent different magmatic pulses. The magmas that produced these cinder cones represent the most enriched magmatic component of Poás volcano. Based on the available geochemical data, we define two magmatic components for Poás: 1) The Sabana Redonda component (TiO2 >1%, relatively enriched in HFSE and other incompatible elements), which is also present in the Paleo-Poás, Poás lapilli tuff y and some Botos crater lavas. 2) The von Frantzius component (TiO2 <0.8%), which is present at lavas from the main crater, von Frantzius cone, Hule maar, and in some Botos crater lavas. Intermediate lavas (TiO2 0.8-1%) are hybrids between these two components. Both components share the same OIB-like source, although the Sabana Redonda component requires a relatively lower degree of partial melting, produced primarily by a decompression mechanism, which may be related with the extension generated within the Poás volcano-tectonic fracture. The von Frantzius component represents magmas produced primarily by flux melting related with the subduction processes. [ABSTRACT FROM AUTHOR]