Mary, the wife of Crown Prince Frederik, was to represent Denmark's royal family at the Lithuanian centennial of statehood events in Lithuania this week.
Denmark's Prince Henrik, husband of Queen Margrethe II, passed away on Tuesday evening after a long disease.
Lithuania's President Dalia Grybauskaitė extended condolences on behalf of the Lithuanian people and on her own behalf on the passing of Prince Henrik.
"Lithuania warmly remembers the visit of Queen Margrethe II of Denmark and Prince Henrik to Lithuania in 1992, and highly values Denmark's and the Royal Family's personal support extended to the Lithuanian people and to re-independent Lithuania," Grybauskaitė said in her message.
Born in Australia, Mary Donaldson and Prince Frederik, the main successor to the throne to replace his mother, married in 2004. After her husband becomes king, she should become the queen of Denmark.