Ranbir, 33, is rumoured to be dating Salman's ex-girlfriend Katrina Kaif.
While the "Bajrangi Bhaijaan" star is still friends with Katrina, he apparently does not share a good equation with Ranbir.
Deepika, 29, was seen promoting "Tamasha" on the reality show and having a good time with the superstar host.
When asked about the reason for his absence, Ranbir said, "Deepika and the marketing team thought 'Bigg Boss' is a big platform to promote the film. But I didn't go for my own personal reasons."
Ranbir, Deepika and Imtiaz Ali were in the capital to promote "Tamasha".
This is the second time Ranbir is collaborating with the director after thier 2011 hit "Rockstar", while it is Deepika's third film with Imtiaz after "Love Aaj Kal" and "Cocktail".