Old-growth forests are often looked at as a reference for naturalness. Analyzing their successional pathways can provide valuable information on the main drivers of succession in the absence of anthropogenic influence. This knowledge could then prove particularly useful for the maintenance of mixed species stands as a management option to counteract potential changes in forest functions under foreseen climate scenarios. The study was conducted in an old growth Quercus petraea-Fagus sylvatica forest in the Runcu Grosi Natural Reserve, western Romania. Main goals of the research were to assess the structure of the old growth forest and understand how the spatial pattern of the two species is shaped by their competitive relationship. We wanted to figure out if the spatial relationship between Q. petraea and F. sylvatica is different between trees belonging to different layers, and how a possible difference can influence their successional dynamics. To accomplish these tasks, living and dead (both standing and lying) trees were mapped in four 0.56 ha plots. The relationship between trees, considering species, vegetative and social status, was analysed through univariate and bivariate point pattern analyses. Spatial structure based on tree size was investigated with Moran’s correlograms and a local indicator of spatial association. The spatial relationship between understory and canopy trees was also assessed using crown cover data to test for differences among the species.