Background: The use of robots for providing support to persons with dementia is very promising. In this paper, we propose an information-support robot for persons with memory and cognitive impairments, using field-based methodology. To date, it is not been made clear why a physical robot is more effective than an on-screen agent in presenting information, or what effect this has on the recipient. Objective: The purpose of this study is to clarify the effect of the form and type of the two devices used in communication. To do this, comparative experiments using a physical robot and a robot agent were conducted with healthy elderly people and person with mild dementia. Method: A communication robot/agent system produced by NEC Corporation, called “PaPeRo®,” was chosen as the platform for this system. The comparative experiment design was a between-group design (robot vs. agent; elderly vs. dementia). Sixteen information tasks were set during an interference task in each case. Result: The results of experiments conducted with 13 elderly people and 5 person with dementia showed that the average rates of information acquisition of a Robot/Agent with mentally healthy elderly people were 65.5%/66.2%, and 62.5%/55.8% for the person with mild dementia. The participants demonstrated awareness, attention, understanding, replies, and actions to the Robot/Agent 43.3%/47.1% of the time for the healthy elderly people, and 45.0%/41.3% of the time for person with dementia. Conclusions: These results suggest that a physical robot is more suitable and more effective than a robot agent for a person who is suffering a decrease in cognitive and attention functions.