Business associations, unions, political parties and professional orders were among groups that asked Monday for particular status at the Charbonneau commission.
Some requested they be given participant status, meaning they would have more powers such as being able to cross-examine witnesses or request that certain witnesses be called.
The inquiry commissioners, led by Quebec Superior Court Justice France Charbonneau, will rule on the requests Thursday.
Denis Houle, who represents an association whose members build roads and participate in large projects, said these associations are suffering and need to defend their interests.
"There are people who act in good faith, there are people who are honest," Houle said.
The Quebec government and the Parti Quebecois also requested the status of participant, while the Quebec Liberals did not ask for any status.
Premier Jean Charest called the inquiry after public pressure mounted increasingly for almost two years following allegations of corruption in the construction industry. He had originally insisted the investigations would be better handled by police.
The commission will begin hearing witnesses on Friday.
Initial testimony will come from government experts on the process of awarding contracts, followed by the former boss of the province's anti-collusion unit, Jacques Duchesneau.