R. de la Llave, R. Obaya Decomposition theorems for groups of diffeomorphisms in the sphere (57K, Latex 2.09) ABSTRACT. We study the algebraic structure of several groups of differentiable diffeomorphism in $\sphere^n$. We show that given any sufficiently smooth diffeomorphism can be written as the composition of a finite number of diffeomorphisms which are symmetric under reflection, essentially one-dimensional and about as differentiable as the given one.