Greek authorities say a tax fraud network ran about 2,000 shell companies, many of them bars and nightclubs, by paying seriously ill people, some recruited outside cancer hospitals, to pose as their managers.
One of the suspects, former model Errikos Petilon, denied any wrongdoing on Sunday.
"This whole thing happening to me is unfair," Mr. Petilon told Mega TV. "I will cooperate with the authorities because I have done nothing illegal. I deny the charge against me."
The case goes to the heart of a problem that has dogged Greece for decades. Widespread tax evasion was one of the weaknesses that pushed the country into its debt crisis and three international bailouts in the 2010s.
The government says digital invoicing and tougher enforcement have since sharply narrowed the gap between taxes owed and taxes collected.
But a wave of high-profile cases in recent weeks, including an alleged 100-million-euro fraud at a national bakery chain, has turned the issue into a political flashpoint less than a year before elections.
According to a months-long investigation by Greece's tax authority and its financial crimes unit, the network used 4,200 tax registration numbers and more than 700 business premises.
Most were in Thessaloniki, Greece's second-largest city, and the nearby resort area of Halkidiki.
Investigators say recruiters approached patients outside Thessaloniki's Theagenio cancer hospital and Athens' Agios Savvas cancer hospital, offering small sums to register as company managers with no real role.
The front men, known in Greek as "straw men," allow the real owners to avoid taxes and debts while staying hidden.
A prosecutor has filed felony charges including running a criminal organization, defrauding the state of more than 120,000 euros ($139,000), forgery and money laundering.
Police arrested 18 people.
Two were released because their cases involve only weapons offenses. The remaining suspects stay in custody until they appear before an investigating magistrate next week.