Previous research has begun to elucidate the physiological impairments associated with dysphagia in patients with dementia, but in order to select the most appropriate targets of intervention we need to better understand consequences of dysphagia. The purpose of this study was to quantify penetration, aspiration, and residue in people with dementia, and confirm if residue was associated with airway invasion on subsequent swallows. Videofluoroscopy clips of sips of thin and extremely thick liquid barium from 58 patients with dementia were retrospectively analyzed. Ratings of swallowing safety, using the Penetration–Aspiration Scale (PAS), and efficiency, using Normalized Residue Ratio Scale in the valleculae (NRRSv) and pyriform sinuses (NRRSp), were made on all swallows. Over 70% of both thin and extremely thick liquid swallows were found to be safe (PAS < 3). Results also revealed that residue was generally more common in the valleculae. However, the proportion of thin liquid swallows with significant NRRSp that were unsafe on the subsequent swallow was significantly greater than the proportion of swallows with significant NRRSp that were safe on the subsequent swallow. As such, there was a 2.83 times greater relative risk of penetration–aspiration in the presence of thin liquid pyriform sinus residue. Future research should determine the impaired physiology causing aspiration and residue in this population.