In 1999 Efimenko won the U-14 division of the
World Youth Chess Championships in
Oropesa del Mar, Spain. In the same year he was a member of the Ukrainian national youth team, which won the U-16 Chess Olympiad in
Artek, Ukraine. Efimenko has won several chess tournaments since then, among them the 2001 Stork Young Masters in
Hengelo, Netherlands. In 2005 he tied for 1st–5th with
Levon Aronian,
Kiril Georgiev,
Alexei Shirov and
Emil Sutovsky in the
Gibraltar Chess Festival. He became
champion of Ukraine in 2006. In 2007, he tied for 1st–6th with
Vitali Golod,
Mateusz Bartel,
Yuri Yakovich,
Michael Roiz and
Mikhail Kobalia in the 16th Monarch Assurance
Isle of Man International tournament. In May 2010, he tied for 1st–2nd with
Victor Bologan in the 40th Bosna International Tournament in
Sarajevo. At the
39th Chess Olympiad, held later in the same year in
Khanty-Mansiysk, Efimenko won the team gold medal and an individual silver playing board 4. In 2015, Efimenko tied for 1st–3rd with
Andrei Volokitin and
Martyn Kravtsiv in the Ukrainian championship in
Lviv. == Personal life ==