The topic of human adult neural plasticity and neurogenesis is of great interest for medical and scientific community, but it is also largely debated. In the last years, an increasing interest has been paid to the olfactory system, and particularly to the plasticity of the olfactory bulb (OB). While the molecular/cellular mechanisms underlying OB plasticity remain a matter of debate, measurements of the OB using magnetic resonance imaging clearly indicate that it is a highly plastic structure. In this review, we present results regarding the plasticity of the human adult olfactory system.