The present work shows some preliminary results of a longitudinal study aimed at validating a psychometric instrument - the Subjective Distance Scale (SDS) - developed to assess the patient's affective nearness/remoteness towards/from the psychiatric treatment in a Day Hospital program. 55 day hospital patients were assessed at different moments of the treatment: At admission they were evaluated by means of the SDS, the SCL-90-R (patient's psychiatric symptoms) and the GAS (patient's mental health level). Institutional therapeutic alliance was assessed one week from admission (IWAI-p) and finally, patient's psychiatric symptoms were retested (SCL-90-R) at the end of the treatment and 3 months from discharge. The main results reveal good psychometric properties of the SDS: its factorial structure partially confirms the dimensions theoretically hypothesised; its internal consistency - total and most of its subscales - reach adequate reliability levels; and related to its predicted validity, the scale correlates with some important aspects of the treatment, like the quality of the early institutional alliance, the symptomatic improvement and the stability of the improvements in time. New studies with larger samples and conducted in additional psychiatric settings are necessary to guarantee the validity and reliability of the scale before it could be used as a clinical screening instrument.