In olfaction, sensitization refers to the amplification of a weak olfactory signal when the stimulus is repeated within a specific time window. This occurs at the level of olfactory sensory neurons (OSNs) where odorant receptors (ORs) are housed. Out of the ~60 ORs in Drosophila melanogaster, sensitization has been observed in only a few types. Therefore, whether the ability to sensitize is a general property of OSNs is still unknown. The mechanism has been partially elucidated, however the regulation of the process in the different neuronal compartments (i.e. soma, inner dendrite, outer dendrite) it is still not clear. In addition, mitochondria could also play a role in OSNs sensitization since they have been shown to shape the olfactory response. In our study we addressed these questions by characterizing sensitization in a set of seven OSNs with different valence and tuning properties. Using a combination of single sensillum recordings (SSR), calcium imaging and pharmacology, we show how the olfactory signal is processed at the periphery, and find that sensitization is not a general property. In our selected OSN population, sensitization is restricted to those with positive valence. Finally, we demonstrate that mitochondria play an active role in sensitization by acting as intracellular Ca²⁺ buffer.