The Swiss Animal Protection (STS) organisation has issued a warning against dubious pet dealers offering animals online.
STS said many dealers were simply trying to get rich at the expense of trustful buyers.
The protection agency said it should be a sign of dubious practices if an online seller offers several different breeds of a dog, for example, or a continuous supply of puppies.
STS said every imaginable animal could be bought over the internet, from tarantula spiders to capuchin monkeys.
In a single day, the organisation counted about 15,000 different offers for around 500 different species - with dogs and cats topping the list - on 15 different websites frequented by the Swiss.
STS said many pets sold via the internet had been maltreated or were sick.
The organisation also warned against buying exotic animals or wild animals from sellers outside of Switzerland since special licences are often required to bring them into the country.
It recommends that potential pet owners visit the breeder prior to a purchase, and to check his or her credentials through a recognised association.