The Louth TD, who has fiercely criticised private healthcare in Ireland, shot down accusations of hypocrisy for travelling to New York for costly laser surgery.
Mr Adams said: "It's a private decision by me. That's my business. And I think those who attack me on that are engaging absolutely in hypocrisy and opportunism."
The Sinn Fein president underwent the procedure last July.
A spokesman for the party confirmed his flights were funded by support network Friends of Sinn Fein and that Mr Adams paid for the surgery himself.
The party has insisted the procedure was to address a painful prostate problem - not cancer.
Despite choosing private care in the US, the TD said he was still strongly opposed to the privatisation of Ireland's health service.
"Obviously the Sinn Fein position and my position is against the privatisation of our health service here on this island, and that's my very, very firm position," he said.
"It should be possible for a citizen to get the type of treatment that they require here. That isn't always possible."
Politicians on both sides of the border, including an SDLP assembly member in the north and Fine Gael TDs, have accused Mr Adams of hypocrisy over the US treatment. Sinn Fein has consistently argued that Health Minister James Reilly wants to privatise healthcare in Ireland.