Butyrylcholinesterase (BChE) genotypes and protein (BuChE) activity, especially in combination with Apolipoprotein E4 (ApoE4), have been investigated as risk factors for developing Alzheimer disease (AD) and may be associated with the rate of progression of cognitive decline. Despite similar pathologic (e.g. amyloid deposition) and neurochemical (e.g. cholinergic deficits) aspects between AD and Lewy body diseases (LBD), scarce data is obtainable about BChE genotypes and BuChE activity in LBD. We measured BuChE activity levels in serum and cerebrospinal fluid (CSF) of 114 LBD subjects (59 of them were demented) and 31 elderly controls. We found higher CSF BuChE activity in males compared to females, and a negative correlation of serum BuChE activity with age and cognitive function. Demented LBD patients, non-demented LBD patients and controls did not differ significantly with regard to serum and CSF BuChE activity. Furthermore, BChE K variant and ApoE4 allele frequencies were determined. The BChE K variant was significantly associated with lower serum activity; the same trend was observable in CSF. The subgroups did not differ significantly with regard to BChE K/ApoE4 occurrence. These data confirm and extend previous results on the relationship between BChE gene and BuChE activity, and argue rather against a major impact of BuChE on LBD-associated pathologies.