Polycyclic aromatic hydrocarbons (PAHs) are among the most studied organic compounds in urban environments, due to their known threat to human health. This study extends the current knowledge regarding the ability of different vegetative parts of different tree species to accumulate PAHs. Moreover, the levels and sources of PAHs in areas frequented by populations susceptible to adverse health effects of air pollution are also evaluated. For this, leaves and barks of Sambucus nigra and Acacia melanoxylon were collected at urban areas in the Andean city of Quito, at seven points near Hospitals and Schools. A methodology for the extraction, purification and quantification of PAHs previously developed for leaves and bark of Sambucus nigra was used and was also evaluated for leaves and bark of Acacia melanoxylon in the present work. The leaves of Sambucus nigra and bark of Acacia melanoxylon showed the highest ability to accumulate PAHs, mainly for heavy and medium molecular weight PAHs, respectively, although the highest incidence of light molecular weight PAHs were found in the leaves of Acacia melanoxylon. Coal combustion, biomass burning, and vehicle emissions were identified as the main PAH sources.