Introduction Abies alba, the second important conifer species in Romania, represents the (co)dominant tree in about 5% of Romanian forests [Barbu I. & Barbu C., 2005]. In the Eastern Carpathians of Romania it frequently forms mixed stands in codominance with Picea abies and Fagus sylvatica. More rarely, it edifi es pure stands. The article’s purpose is to present a numerical classifi cation of Abies alba communities, to detect the diagnostic species for the distinguished vegetation units and to detect the main ecological factors infl uencing their fl oristic composition. Material and methods In order to classify and characterize the vegetal communities with silver fi r, a set of 215 relevés was selected from literature. Data analysis was realized using the Flexible beta agglomerative hierarchical algorithm and Bray-Curtis distance. Determination of the diagnostic species was realized using the binary indicator value coeffi cient [Dufrêne & Legendre, 1997]. Detrended correspondence analysis has been performed in order to characterize vegetation from an ecological perspective. Results and discussions Numerical techniques generated clusters (groups) which could be related to vegetal associations described in literature based on diagnostic species analysis. They were integrated in the next syntaxa conspectus: VACCINIO-PICEETEA Br.-Bl. in Br.-Bl. et al. 1939 ATHYRIO-PICEETALIA Hadač 1962 Abieti-Piceion (Br.-Bl. in Br.-Bl. et al. 1939) Soó 1964 Hieracio transsilvanico-Abietetum (Borhidi 1971) Coldea 1991 QUERCO-FAGETEA Br.-Bl. et Vlieger in Vlieger 1937 FAGETALIA SYLVATICAE Pawlowski in Pawlowski et al. 1928 Symphyto cordati-Fagion Vida 1963 Pulmonario rubrae-Fagetum (Soó 1964) Täuber 1987 Detrended correspondence analysis separated the forest communities of increased altitudes, adapted to more restrictive environment conditions from forest communities of lower altitudes edifi ed by plant species with the ecological optimum in a higher range of temperature, developed on soils richer in nutrients. Conclusions Numerical analysis of the silver fi r communities from Eastern Carpathians (Romania) has as result their classifi cation in 2 major vegetation types. Based on the identifi ed diagnostic species they can be assigned to the vegetal associations from phytosociological literature. Altitude, soil pH and nutrients are the main factors infl uencing the fl oristic composition of these plant communities.