The group, which supplies close to 400 independent retailers through its wholesale arm, also owns and operates 60 c-stores and forecourts in the province.
In the past 12 months it has opened 17 new stores under the Spar, Eurospar, Vivo and Vivo-xtra fascias. The group also launched a new c-store format, Vivo Essentials, of which more than 40 have now opened across Northern Ireland.
The group has promised to build on its success by investing more than £20m in 2008 to help develop both its independent and company-owned stores.
Henderson sales and marketing director Paddy Doody said: "Despite growing pressure on the convenience store sector, this is an encouraging time for the group and its independent retail partners."