In this paper, we will for shift spaces having a certain property (*), show that the first cohomology group is a factor group of Matsumoto's K0-group. We will also for shift spaces having an additional property (**), describe Matsumoto's K0-group in terms of the first cohomology group and some extra information determined by the left special elements of the shift space. We determine for a broad range of different classes of shift spaces if they have property (*) and property (**) and use this to show that Matsumoto's K0-group and the first cohomology group are isomorphic for example for finite shift spaces and for Sturmian shift spaces. Furthermore, the ground is laid for a description of the Matsumoto K0-group as an ordered group in a forthcoming paper.