A cross-sectional study of the profile of psychiatric symptoms and their relationships to medications, executive performance, and excessive daytime somnolence (EDS) was conducted on 1351 consecutive Parkinson's disease patients without dementia (PD-ND). Ratings were: neuropsychiatric inventory (NPI); hospital anxiety and depression scale (HADS); executive performance (semantic, phonemic, and alternating verbal fluencies); and the Epworth sleepiness scale (ESS). Eighty-seven percent of the subjects reported at least one psychiatric symptom. The most common were depression (70%), anxiety (69%), apathy (48%), and irritability (47%). Fifty percent of the patients had HADS-depression scores ranging from possible (8-10; 22%) to probable (≥11; 28%) depression. Executive impairment was found in 41% and EDS in 26% of subjects. All considered variables were significantly more common with longer duration and more severe disease. Only depression appeared to be influenced by type of medication, being less prevalent among patients treated with DAs. Five NPI clusters were identified among patients scoring ≥1 on the NPI (87.3%): patients exhibiting predominantly apathy (12.7%), psychosis (3%), depression (13%), anxiety (15.6%), and "low-total NPI" (43.2%). Neuropsychiatric symptoms are common in nondemented PD patients suggesting that they are an integral part of PD from the beginning of the disease and appears more related to disease progression than to the type of antiparkinsonian medication. Apathy emerged as an independent construct in PD-ND, indicating the need to address specific therapeutical approaches targeted toward this particular symptom. © 2008 Movement Disorder Society.