This will all depend on what type of "man boobs" you have.
Holding fatty tissue in that area indicates you have an estrogen dominance/low testosterone problem going on.
This can be caused by many things but, If it is still "soft" and has not hardened over time (true gynocomastia aka bitch tits is only removable in most cases with surgery) then you can reduce your bodyfat levels as well as use an anti-estrogenic compound for a brief time (DIMM is one you can get at GNC or your local supplement shop) along with certain habit changes and implementation of some lifestyle changes such as adding in resistance training (weights) as part of that change.
E-GO 2018
P.s. You can't do chest exercises to get rid of "man boobs" ...only overall fat loss will do this. You cannot spot reduce fat. It's hormonal.
Here are a couple of articles I have written on this subject on quora.com. https://www.quora.com/How-can-I-get-rid-of-gynecomastia-caused-by-steroids/answer/Eric-Morrison-18?share=ab29e532&srid=FQlw
