Owned by Bell Media, the station airs a hot adult contemporary format.

[3] CHUM-FM started broadcasting on September 1, 1963, with an ERP of 18,000 watts and a transmitter and studio at 1331 Yonge Street.

The station featured many famous Canadian radio personalities such as Larry Green, Walter Michaels, Steve Harris, Pete and Geets, Larry Wilson, David Marsden, David Pritchard and actor Rick Moranis.

Former CHUM President Jim Waters was inducted into the Music Industry Hall of Fame that same evening.

The new building is adjacent (and connected) to Bell Media's headquarters at 299 Queen Street West (which also formerly housed the studios of Citytv).

[19][20] On September 10, 2010, Bell Canada announced plans to re-acquire 100% of CTVglobemedia's broadcasting arm, including CHUM Radio.

[22] On June 22, 2018, the station underwent a major rebranding as part of an effort to appeal more strongly to women, including a new logo (amending its brand to CHUM 104.5, as opposed to 104.5 CHUM FM), a generally hotter music direction, as well as a stronger emphasis on social media and community interaction.

[23] CHUM-FM's current host lineup includes Marilyn Denis, Jamar "J. Niice" McNeil, Ashley Greco, Josie Dye, Ruby Carr, Taylor Kaye, Peter Kash, and Aiko Iwashita.

On October 25, 2018, Ashby announced that he would retire from the morning show effective December 6, after 50 years with CHUM-AM and CHUM-FM.

As of Spring 2018, CHUM-FM is no longer broadcasting in HD, with the sub-channels moving to sister station CKFM-FM.