People with incomes just above the medical card threshold are being left in a "twilight zone" with poorer health outcomes.
That's one of the findings of a Europe-wide report on healthcare published by the think tank TASC.
It warns of high levels of inequality in the Irish healthcare system.
The study says Irish people in higher income groups were 21% more likely to have good health, compared to those in lower income groups.
Shana Cohen from TASC says that's partly because people with health insurance get quicker access to treatment.
She said: "Those in the higher income are the highest in the EU in terms of self-reporting satisfaction with their health - but those on the lower income are not higher than other countries.
"You're seeing a difference between those on a higher income and those on a lower income - and that reflects their access to all services."
She added: “What this report makes very clear is that people with private health insurance in Ireland have a much better chance of getting the health services they need, and getting them quickly."