Dimon choked up as he recounted his conversations with Lee at a memorial service on Monday. Lee, a vice chairman in investment banking at JPMorgan, died unexpectedly on Wednesday morning after working out on a treadmill and growing short of breath. He was 62 years old.

The JPMorgan CEO said Lee had talked many times about being 11 years old when his father had died unexpectedly. Dimon said that experience may explain why Lee had an intense desire to prove himself and to love and be loved.

Dimon, speaking as though he was addressing Lee, said, "You lived every day – and in fact went about every conversation – as if it might be your last. You took nothing for granted and left nothing unsaid."

Mourners nearly filled St. Patrick's Cathedral.

Lee, one of Wall Street's most consistently visible investment bankers on big deals for the past 30 years, would have been pleased to see so many people in the cathedral, his son Jamie Lee said during one of three eulogies at the service.

Among those who attended were Jeff Immelt, chairman and chief executive of General Electric Co, Steve Schwarzman, chairman and chief executive of The Blackstone Group, fund manager Bill Ackman of Pershing Square Capital Management and David Rubenstein, co-founder of The Carlyle Group.

JPMorgan executives included consumer bank chief Gordon Smith, commercial bank chief Doug Petno and Mary Erdoes, head of the asset management business.

Mike Bloomberg, former New York City mayor, and television journalist Charlie Rose were among 46 honorary ushers.

Cardinal Timothy Dolan said that Lee, in addition to giving to Catholic charities, had been a mentor to high school students from the inner city as well as to investment bankers.

(Reporting by David Henry in New York; Editing by Cynthia Osterman)