Purpose: To study the influence of concomitant Alzheimer's disease (AD) pathology in dementia with Lewy bodies (DLB) on dopamine transporter (DAT) and serotonin transporter (SERT) availability, using 123I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (123I-FP-CIT) single photon emission computed tomography (SPECT). Methods: Based on their cerebrospinal fluid biomarker profile, fifty-two patients with probable DLB were divided in a group with (DLB/AD+, N = 15) and without concomitant AD-pathology (DLB/AD-, N = 37). We conducted atrophy-corrected region of interest (ROI) analyses comparing binding ratios (BRs) in the DAT-rich striatal and SERT-rich extrastriatal brain areas (amygdala, hippocampus, thalamus, midbrain and pons). Results: DLB/AD+ patients had significantly lower 123I-FP-CIT BRs in the left amygdala, and a trend was seen in the right hippocampus. Groups did not differ significantly in striatal 123I-FP-CIT BRs, neuropsychiatric or motor symptoms. Motor symptoms correlated negatively with striatal DAT BRs. Conclusions: DLB/AD+ patients may have lower SERT binding in limbic brain regions than DLB/AD- patients, possibly indicating faster neurodegeneration in mixed pathology.