An important goal in plant community ecology is to understand how species traits determine demographic performance. Several functional traits have been shown to correlate with growth and mortality rates in trees, but less is known about how the relationships between functional traits and demographic rates change with tree size. We examined the associations of functional traits with growth and mortality across co-occurring tree species in subtropical and tropical tree communities. To quantify size-dependent changes in growth and mortality, relative growth rate and mortality were estimated as a function of stem diameter using hierarchical Bayesian models. These rate estimates were then correlated with functional traits at a range of stem diameter classes. Based on our results from many co-occurring species in different tree communities, we will discuss to what extent size-dependent changes in demography or functional traits affect their statistical relationship and our general biological understanding of these relationships in tree communities.