Pollen from different tree and grass species represent the greatest inducers of type I allergy worldwide. Oriental plane trees, as Platanus orientalis, are an important source of airborne allergens in cities of the southwest Asia and southeast Europe. This study was aimed to identify relevant allergens of P. orientalis pollen and to ascertain whether P. orientalis allergens have cross-reactivity with related plane trees, such as Platanus acerifolia and Platanus occidentalis pollen components. Nineteen patients with a clinical history of reaction to P. orientalis pollen and a positive skin-prick test (SPT) to P. orientalis pollen extract were included in this study. Identification of IgE-binding proteins in Platanus pollen extracts was elucidated by immunoblotting using sera from P. orientalis pollen-sensitive patients. Cross-reactivity studies among P. orientalis allergens and relevant species was evaluated by immunoblot-inhibition and ELISA inhibition assays. All the patients were polysensitive and exhibited positive SPT to grass and tree pollen allergens. The IgE-binding pattern of P. orientalis pollen extract was well defined. The inhibition experiments showed that the capacity of P. occidentalis was greater than P. acerifolia pollen extract in preventing the reactivity of immobilized P. orientalis pollen extract with the IgE antibodies of patients. The 28-kDa molecule was the most frequent allergen among nine IgE-binding proteins of P. orientalis pollen. The IgE-reactive components of P. orientalis pollen showed a higher level of cross-reactivity with P. occidentalis pollen in comparison with P. acerifolia pollen.