Electronic Journal of Differential Equations, Vol. 2013 (2013), No. 153, pp. 1-13. Title: Psi-exponential dichotomy for linear differential equations in a Banach space Authors: Atanaska Georgieva (Univ. of Plovdiv, Bulgaria) Hristo Kiskinov (Univ. of Plovdiv, Bulgaria) Stepan Kostadinov (Univ. of Plovdiv, Bulgaria) Andrey Zahariev (Univ. of Plovdiv, Bulgaria) Abstract: In this article we extend the concept psi-exponential and psi-ordinary dichotomies for homogeneous linear differential equations in a Banach space. With these two concepts we prove the existence of psi-bounded solutions of the appropriate inhomogeneous equation. A roughness of the psi-dichotomy is also considered. Submitted March 28, 2013. Published July 02, 2013. Math Subject Classifications: 34G10, 34D09, 34C11. Key Words: Dichotomy for ordinary differential equations; psi-dichotomy; psi-boundedness; psi-stability.