Reiki and massage are different. By definition, massage is a form of tissue manipulation for healing/well-being purposes. Traditional Reiki, as practiced in the United States, does no tissue manipulation. The hands are motionless on any place where they are placed. There is no pressure, stroking, rubbing, squeezing, tapping, or other form of manipulation, even though Usui did mention these in his original system*. Whereas massage is generally conducted on a nude, draped client, Reiki is usually given to a fully clothed client. Massage practice may use oils and other devices; Reiki uses neither. Massage tries to mobilize and/or relax tissues through increased blood and lymph circulation and the reduction of tense areas. Reiki provides simply the chance for subtle energy to flow quietly through the practitioner to the client. Both modalities face substantial legal problems for the practitioner.
Some states in the USA have attempted to regulate Reiki by trying to call it massage. Such attempts, whether legislative or administrative, have ultimately failed in court tests, or are in the process of being defeated [as in Florida]. Notable states are Texas, New York, and Florida. Some states do not even regulate massage [Vermont is such a state - I could practice massage in this state simply because a client asked me to use it].
Reiki Hand positions, themselves, rarely provide a question about massage. [see below], although certain ones may be considered to be outside the areas which are used for massage in certain states, thereby creating a violation of rules which some Reiki practitioners face in those states which do regulate Reiki as massage. Reiki is combined with massage, at times, in those states where massage is not regulated. Such usage must be considered to be very unusual, and should be done with the utmost consideration and sensitivity, as well as with a view to all legalities involved. [Actually, Reiki will always flow anyway when both hands are placed on a person. This obviously also happens during massage. What would be different in massage is that the Reiki hand positions would not be used. Many massage therapists choose to learn Reiki, not so much as a single primary modality, but to provide the most relaxing traditional massage possible, due to the automatic flow of Reiki which happens when the therapist puts both hands on the client.]
*[There is information that Usui did use some very gentle tissue manipulation in the application of Reiki at times. He mentions various so-called "non-traditional" uses - patting lightly, stroking gently, pushing/pressing, and the use of the breath and the eyes [there is a history of this kind of manipulation in Tibetan massage and Taoist massage]. These uses are not employed in the United States by most Reiki practitioners, to avoid any similarity to massage. In fact, most Reiki practitioners in the United States are unaware of these additional Usui methods. In addition, massage in the West is used to relax muscles and to enhance flexibility. In the East, massage is used most often to mobilize and direct a better flow of Ch'i/Ki to permit healing.]