Grapevine downy mildew is an important disease affecting crop production and causing severe losses. To identify genotype-dependent responses towards this pathogen and to explore the molecular mechanisms involved in grapevine-P. viticola resistance, we have conducted a proteomic analysis of leaf samples from resistant and susceptible grapevine genotypes prior and post-inoculation with the pathogen. Proteins were analyzed by quantitative two-dimensional differential gel electrophoresis (2D-DIGE). The analysis able to identified 50 unique proteins. Functional analysis showed that photosynthesis and metabolism were the main categories differentiating genotypes at 0h and that P. viticola-responsive proteins were mainly involved in photosynthesis, carbohydrate metabolism, stress and defense responses and redox homeostasis. ROS production, total antioxidant capacity and lipid peroxidation on both genotypes were determined and together with the proteome data suggest that Regent presents a strict balance between ROS control and signaling leading to plant cell death activation. Our data reveals the genotype-dependent modulation of plant metabolism and defense responses providing new insights into underlying molecular processes of grapevine resistance against the downy mildew fungus.