In this paper, we introduce a hybrid modeling framework for creating complex objects. Our system relies on an extended CSG tree that assembles skeletal implicit surfaces and polygonal meshes in a coherent fashion: we call this structure the HybridTree. Editing operations are performed by exploiting the complementary abilities of both implicit and parametric surface representations. Implicit surfaces are powerful for combining shapes with Boolean and blending operations, while polygonal meshes are well-suited for local deformations such as FFD and fast visualization. The evaluation of the HybridTree is performed on the fly either through field function queries when the implicit form is required, or through a mesh creation process which is specific and optimized for every kind of node. Both types of queries are achieved in a complete transparent way for the user.