The pair appear on alternative covers of a special issue of TV Guide in honour of the poll.
Dempsey plays Derek "Dr. McDreamy" Shepherd in US medical drama Grey's Anatomy, while Love Hewitt, 29, stars as Melinda Gordon in Ghost Whisperer.
Dempsey, 42, was praised by the magazine for his “beautiful head of hair, piercing eyes and dazzling smile".
Meanwhile, Love Hewitt's on-screen husband David Conrad said his co-star deserved to top the list, saying: "In the three years that we've been filming, there's always a moment when I just go, 'Wow, that's a really beautiful woman.'"
The list also includes Grey's Anatomy star Justin Chambers and Ugly Betty's Vanessa Williams, along with Taye Diggs (Private Practice), Eva Longoria Parker (Desperate Housewives) and Josh Holloway (Lost).