While Peru has pledged to reduce greenhouse gas emissions, oil palm plantations are currently under expansion in the Peruvian Amazon at the risk of forest conversion. This study aimed to characterize the structure and composition of remnant disturbed forests adjacent to oil palm plantations in the Peruvian Amazon region of Ucayali, to further determine the carbon stock loss/gain from such transition. The thesis was based on data collected by CIFOR in a 2015 field campaign, which included four forest plots and six oil palm stands. The latter ones using a space-for-time substitution approach to assess the carbon stock change over a rotation period. All carbon pools were analyzed and compared over the land use transition. In the case of oil palm plantations, per pool time-averaged carbon stocks were developed from estimated growth models in a 30 year-old rotation. Forest composition and structure analysis at the study site evidenced past anthropogenic disturbance, probably due to previous logging activities. Species characterization did not reveal deterministic differences between plots and all presented a certain level of species homogenization. Previous forest practices showed a negative effect in composition and structural parameters, the mean basal area was found to be 22 (SE 1.4) m2 ha -1. Overall, the conversion from disturbed forests to oil palm plantations resulted in a carbon debt scenario, as forests presented a total carbon stock of 140.7 (SE 5.8) Mg C ha-1 and the time-averaged carbon stock of oil palm plantation 74.3 (SE 2.2) Mg C ha-1. Above ground carbon was the main contributing pool; followed by soil organic carbon and necromass. Remnant disturbed forests at the study site are at systematic risk of conversion. This research contributes to the current land planning discussions on where to settle new areas for oil palm production. In terms of carbon footprint, logged forest and secondary forests should be excluded from the scope. Instead, conversion should be directed to highly degraded lands such as pastures and shrubs, where further studies are still needed.