Cool Stars 14 - Submitted Abstract # 82 This version created on 05 October 2006 The Lambda Orinos Star Forming Region: the Spitzer Perspective David Barrado y Navascues, LAEFF-INTA John R. Stauffer, IPAC Maria Morales-Calderon, LAEFF-INTA The Head of Orion is a complex star forming region which includes a young open cluster (Collinder 69, about 5 Myr), two dark clouds (Barnard 30 and Barnard 35, with younger populations) and another younger areas (LDN 1588 and LDN1603). We have observed one square degree in each of these regions with Spitzer in order to study the stellar and substellar population. These data have been complemented with optical and near infrared photometry and spectroscopy. Among the properties we have analyzed are the Initial Mas Function for each association, circumstellar disks and their properties, and the fraction of members with disks, and tried to explain all these properties in the context of the differences in the local environment and the evolution. ----------------------------------