The Time and Weight Estimation test (STEP) and the Cognitive Estimation Task (CET) are two recently devised tests for the assessment of cognitive estimation. In the present study, we compared their performance in 30 non-demented idiopathic parkinsonian (PD) patients, also evaluated with the Frontal Assessment Battery (FAB) as an index of executive impairment, with the aim of verifying the putative frontal circuitry of cognitive estimation processes. Six patients (20%) showed a pathological performance on either or both tests. After division of the PD sample into tertiles based on the FAB score, no significant difference was detected by either estimation test. Furthermore, the two questionnaires were unrelated to each other. Thus, deficits of cognitive estimation ability appear to be mild in PD without dementia and do not correlate with executive impairment. Unexpectedly, the CET and the STEP seem to have no unique underlying construct.