Yes, but this is subject to an important qualification. In some cases, what the person in question is deluded about is the truth; in other cases, what the person in question is deluded about is not the truth itself but the amount of emotional weight to be given to a given truth.
A schizophrenic may believe that aliens are monitoring her phone conversations: this is a delusion about the truth.
When an obsessive-compulsive is deluded, it is not in this way. He may obsess about the B he received in some class, his delusion being that this grade is deeply important, when, in actuality, it is only moderately important.
With the schizophrenic, the delusion is direct, meaning that it concerns her grasp of what is the case in the external world. With the obsessive-compulsive, the delusion is indirect, meaning that it concerns the amount of weight to be given to what he correctly perceives to be the case in the external world.
When a disorder involves a direct skewing of awareness, it is a psychosis; and when it involves an indirect skewing of awareness, it is a neurosis.