Changes in cerebral blood flow (CBF) have the ability to confound structural and quantitative MRI studies. Caffeine is widely consumed and leads to strong decreases in CBF. Moderate caffeine users were scanned before and after caffeinated and decaffeinated coffee over two separate days. Percentage change in CBF maps, quantitative T1 maps, and estimates of grey matter volume (GMV) were assessed for the caffeinated coffee and decaffeinated coffee days. Robust decreases in CBF were observed, along with changes in T1 maps and estimates of GMV. Caffeine intake should be considered in studies relying on structural and quantitative MRI measures.