First Minister Nicola Sturgeon said she was "horrified" to read reports of landlords offering rent-free accommodation in return for sex.
The Herald newspaper reported that the website Craigslist featured men across Scotland offering flats to women for "favours" and "romance".
Ms Sturgeon told MSPs the housing minister had written to the website asking them to take action.
She said such landlords would not pass a fit and proper person test.
However, the first minister added that these arrangements were likely to be "informal" so the landlords would not be part of the government's registration scheme.
At First Minister's Questions at Holyrood, Labour MSP for Mid Scotland and Fife, Claire Baker, asked the first minister for her response to reports of sexually exploitative behaviour in the private rented housing sector.
Ms Sturgeon said: "I was horrified to read the reports that the member refers to and the minister for housing (Kevin Stewart) has already written to the website concerned, that hosted these adverts, asking them to take action."
She added that poverty and inequality can often leave people vulnerable to being exploited.
"Any person always has the right to refuse to consent to sexual activity and forcing someone, in any way, to participate in sexual activity is a crime," she said.
"We continue to keep all laws under review to ensure they are fit for purpose in tackling what I think are unacceptable behaviours."
No formal tenancy
Ms Baker said there was no way of knowing how many tenants in Scotland had such arrangements.
She said: "The practice opens the door to vulnerable tenants who are already facing homelessness and poverty to finding themselves in commercially-exploitative arrangements."
The first minister said: "Where landlords are behaving unacceptably then clearly there are provisions to seek to deal with that.
"I suspect in cases like the one she is highlighting often the problem will be that there is no formal tenancy agreement.
"These are informal arrangements, which does not make them any more acceptable, but sometimes that will be one of the challenges. These are not formal arrangements where there is a recognised and registered landlord."
Green MSP Patrick Harvie said he was aware that not all such cases involved a registered landlord.
But he added: "Isn't it pretty clear that any such exploitative arrangements should lead to an automatic fail of the fit and proper person test and revocation of any existing landlord registration."
Nicola Sturgeon agreed, saying: "I struggle to see how anyone who placed an advert of this description would pass the fit and proper person test."
She said the housing minister would continue to investigate the matter.