In 1980, "Magill" described him as having critically supported a pro-Soviet line on every 'major issue'. In 1991, O'Riordan's wife Kay Keohane of Clonakilty, County Cork died at their home aged 81. He continued to live in their family home before moving to Glasnevin in 2000 to be close to his son Manus who lived nearby. In 1999, he described himself as an atheist and believed that communism would rise again. He lived there until falling ill in November 2005 and was taken to the Mater Hospital. His health rapidly deteriorated and he quickly developed Alzheimer's disease. Soon afterwards he was moved to St. Mary's Hospital in the Phoenix Park where he spent the final few months of his life, before his death at the age of 88. Then Labour Party leader Ruairi Quinn praised O'Riordan after his death, saying; ""As leader of the Labour Party I had the honour of ensuring he received a special citation at our 2001 national conference Michael O'Riordan stood out against the tide of Irish conservatism and clerical domination that kept Ireland backward and isolated in the 1930s, 1940s and 1950s.""