This research addressed the introduction of a computerized decision support system for drug monitoring to be used by registered nurses in nursing homes. The system was introduced, and its effects were evaluated over the period of 1 year; however, at the end of 1 year, the implementation was not successful in all the participating settings. The aim of this study was to identify the conditions needed for the successful implementation of a computerized decision support system from the registered nurses' perspective. Two case sites were purposively selected based on the implementation's success in one nursing home, but not in the other. Focus group discussions were performed, one in each setting, with eight registered nurses. An inductive thematic analysis was conducted. The findings revealed six themes illustrating the registered nurses' views about the conditions needed: need to see benefits, have the time and take the time, curb administrative hassle, collaboration at all levels, stated responsibility, and requirements set from managerial positions. The most outstanding findings, when compared with the previous implementations of nursing informatics, involved collaboration and the view of drug monitoring responsibility in relation to themselves and the physicians.