The paper consists of two parts. In the first one the general solutions of two functional equations of cubic type are given:
(where is a fixed integer). In the second part the stability in the spirit of Hyers, Ulam, Rassias and Găvruta of the functional equation
(where are fixed integers such that , , , ) is given for functions mapping a topological vector space into a Banach space. Both real and complex case is considered.