International audienceIn this paper we study Lie-admissible structures on Witt type algebras. Witt type algebras are Γ -graded Lie algebras (where Γ is an abelian group) which generalize the Witt algebra. We give all third power-associative and flexible Lie-admissible structures on these algebras. In particular we generalize some results on the Witt algebra. After describing the second scalar cohomology group of Witt type algebras, we investigate third power- associative and flexible Lie-admissible structures on the central extension of some Witt type algebras. Finally we study a left-symmetric structure induced by a symplectic formfor some Witt type algebras