Rosenkopf and Nerkar (2001) examined the relationship between patents with a boundary-spanning exploration of organizations and technological domains and their impact on subsequent technological evolution, using patent data for optical disks as the technological domain. However, the results of their analysis will be affected by the size of the technological domain itself. Therefore, this study analyzes and compares (a) vector control technology for electric motors and (b) the larger technology domain that includes (a). The results indicate that in the case of (a), vector control technology, even when a boundary-spanning exploration is conducted, there is some outside impact, but no domain impact. By comparison, in the larger technology area (b), there was some domain impact, but less outside impact. In other words, the hypotheses were partially supported for vector control technology in electric motors; however, the wider the technological domain, the stronger the domain impact and the weaker the outside impact tended to be, and the impact is dependent on the granularity with which the technology field is defined.