Background: The histology and pattern of spread in lobular breast cancer has presented challenges in estimating extent of disease by traditional imaging methods. ¹⁸F-FES is an estrogen analogue PET imaging tracer which measures tumor ER expression at multiple tumor sites simultaneously. We compared quantitative FES-PET and clinical FDG-PET SUV uptake between patients with metastatic lobular and ductal carcinoma. Methods: We retrospectively compared FES and FDG SUV uptake between ER+ lobular and ductal metastatic breast cancer patients (199 ductal, 44 lobular) enrolled in various studies at our institution. Up to nine lesions in each patient were evaluated by FES SUVmax and/or FDG SUVmax for a total of 619 lesions in FES images (n = 509 ductal, n = 110 lobular) and 466 lesions in FDG images (n = 378 ductal, n = 88 lobular). Using linear mixed-effects models, we assessed differences between lobular and ductal histologies in both FES SUVmax and FDG SUVmax. Overall survival (OS), from time of FES-PET scan to death, was evaluated between histologies using Kaplan-Meier curves and the Log-Rank test. Results: Among metastatic breast cancer patients with positive FES scans, approximately 10% of patients with ductal histology and 9% with lobular histology had absent FES uptake in at least one lesion. Mean (range) SUVmax in FES and FDG respectively for ductal was 3.48 (0.32, 20.5) and 5.2 (1.1, 26.7) and for lobular was 3.34 (0.61, 9.62) and 4.42 (1.09, 20.0). Difference in FES and FDG SUVmax between histologies was marginal and non-significant. On the natural log scale, lobular carcinomas demonstrated a higher SUVmax (Difference = 0.05, 95%CI = [-0.16, 0.26], p = 0.63) and a lower FDG SUVmax (Difference = -0.53, 95%CI = [-1.61, 0.56], p = 0.34. Following FES-PET imaging, patients with ductal carcinomas had a lower, non-significant median survival time (2.97 vs. 3.03 years, p = 0.81). Conclusions: In the metastatic setting, FES and FDG uptake in multiple lesions in ER+ lobular breast cancer patients did not statistically differ from ductal breast cancer. Metastatic lobular breast cancers have similar FES and FDG avidity to metastatic ductal tumors, suggesting these patients may benefit from similar diagnostic and treatment algorithms.