  Let C be triangulated category and X a cluster tilting subcategory of C.
Koenig and Zhu showed that the quotient category C/X is Gorenstein of
Gorenstein dimension at most one. The notion of an extriangulated category was
introduced by Nakaoka and Palu as a simultaneous generalization of exact
categories and triangulated categories. Now let C be extriangulated category
with enough projectives and enough injectives, and X a cluster tilting
subcategory of C. In this article, we show that under certain conditions the
quotient category C/X is Gorenstein of Gorenstein dimension at most one. As an
application, this result generalizes work by Koenig and Zhu.
