Robert M. Greenwood, 78, a retired executive of Merkle Press Inc. and Publishers Inc. who founded his own advertising sales company here, died of congestive heart failure Thursday at Providence Hospital.

Mr. Greenwood began his career in 1923, as a sales representative for the National Publishing Co. In 1947, he joined the sales department of Merkle Press Inc. He was executive vice president of Merkle Press and senior vice president of its parent company, Publishers Inc., now the Pubco Corp., when he retired in 1968.

In 1948, he founded the Advertising Novelty Company Inc. of Washington, an advertising specialty sales firm.

He was a member and former president of the Office and Professional Employes International Union Local No. 2 and was credited with establishing the local's credit union.

Mr. Greenwood, who was born in McKeesport, Pa., had lived in Washington for the past 75 years. He graduated from old Business High School and earned a law degree from National University School of Law, now part of George Washington University.

He was a member of the Grand Lodge of Free and Accepted Masons of D.C., Mount Pleasant Lodge No. 33, the Scottish Rite, the Albert Pike Consistory and Almas Temple. He also was a 35-year member of Congressional Country Club.

Survivors include his wife, Estelle, of Washington; a daughter, Greta Ann Garrison of Silver Spring; two sisters, Elsie Maxwell of California, and Marie Ward of Drum Point, Md., and three grandchildren.