New figures released yesterday revealed more than 15,000 cases where patients had claimed free treatment to which they were not entitled from NHS dentists and opticians.
Counter Fraud Services (CFS) investigators recovered £538,000 from these patients, but there are fears the problem is much greater.
Two health boards failed to reveal their figures and it is estimated NHS Scotland loses up to £110 million every year through frauds of all types, from erroneous claims for free treatment to staff deceptions.
Jackson Carlaw, health spokesman for the Scottish Tories, said: "People who defraud the NHS may not think it, but they are putting lives and jobs at risk.
"Stealing from hospitals is the lowest of the low, and something we can ill afford in times like this.
"NHS Scotland estimates more than £100m is lost each year through this. New hospitals could be built for such a price, and swathes of nurses hired."
Every year the counter fraud arm of the Scottish NHS double checks tens of thousands of patient claims for free dental and ophthalmic services.
The data shows the number of people who received free treatment when they were not entitled to it has grown over the last three years.
In 2009-10, there were 4994 incidents detected and £152,000 recovered. In 2010-11, there were 5238 incidents detected and £175,000 recovered, and, in 2011-12 there were 5398 incidents detected and £211,000 recovered.
However, Counter Fraud Services said that many people have not deliberately deceived the health service but made a mistake.
It cited the example that only patients in receipt of certain benefits are entitled to free eye and dental care.
When the anomaly is picked up, patients are asked to cover the cost of the service they received, which could range from £37.10 for optical care to £385, the maximum bill for NHS dental treatment.
Patients who do not respond within 28 days face the prospect of a fine which could escalate up to £100.
A spokesman for Counter Fraud Services said: "CFS is committed to reducing fraud and corruption in NHS Scotland and to building and promoting a culture in which staff, patients, contractors and the wider public regard fraud against the NHS as totally unacceptable."
The Scottish Conservative Party uncovered the scale of fraudulent and erroneous claims for free care using the Freedom of Information Act.
NHS Greater Glasgow and Clyde, the country's largest health board, had 6985 cases between 2009-12. NHS Lothian had 2225 and NHS Lanarkshire 1646. NHS Ayrshire and Arran and NHS Grampian failed to supply the figures.
Mr Carlaw said: "I urge the courts to come down on such individuals who knowingly rob from the NHS in the most severe way they can, so those considering such a move can be left in no doubt of the consequence that awaits them."
A Scottish Government spokeswoman said: "Any fraud against the health service is unacceptable and there must be zero tolerance of fraud. NHS fraud is not a victimless crime and whether committed by staff, patients, clinicians or contractors, NHS fraud takes money away from where it's needed most."
