The article presents the probable evolution of a soul/deity (Tib. bla/lha) idea complex and the various contexts in which the term ‘deity’ appears in Tibetan beliefs and culture. The pantheon of deities supposed to help people in everyday situations derives from local pre-Buddhist beliefs. These native beliefs were joined by concepts taken from Indian Buddhism. The early Buddhism did not know the concept of deity, however Mahāyāna, distinguishing several planes of manifestation of an enlightened being, started to grant a subtle level of existence to, among others, eminent disciples of the Buddha who reached the end of the spiritual path, as Avalokiteśvara for example. The Tantric current, popular in Tibet, introduced the idea of a personalized deity as the symbol or representation of the ultimate reality: a deity constituting the personal, ideal image of a Tantric practitioner and the object of his contemplation. Furthermore, the author analyzes the way of existence attributed to the deities by the main philosophical schools, as well as the functions of the different types of Tibetan deities.