Smith, 29, is the Vikings longest serving player having been with the club since their last season in Super League in 2005.
Earlier this week, Doran was named in the Championship Team of the Year while full back Yates and utility player Strong are both products of the Widnes academy system.
Sporting Director Terry O’Connor said: “Mark Smith has given us six years of outstanding service and has been a stand-out performer throughout.
“The same applies for Lee Doran who has offered the team a great deal and has always shown a great appetite for work, as his team mates will tell you.
“Scott Yates and Matt Strong are two youngsters who have worked their way through the in-house systems here at the club but unfortunately, for whatever reason, things simply haven’t worked out as expected for all parties.”
The Vikings face Barrow in the Championship play-offs a week on Sunday with uncertainty also clouding the future of star half-back Anthony Thackeray, who rejected a new deal at Widnes amidst interest from a host of Super League clubs.