During times of rising inflation, companies commonly reduce the amount of product they sell for the same price.
The practice is known as "shrinkflation" and consumers are noticing it at the supermarket, according to the Consumers' Union of Finland.
More than 700 consumers responded to the union's call for people to share their shrinkflation experiences in an online questionnaire.
Paula Pessi, the union's communications chief, said the survey revealed that many consumers are well aware of the practice.
Responses to the questionnaire revealed that certain product categories are being affected by shrinkflation, particularly pet foods.
Companies think consumers are fools and assume they won't notice shrinkflation.
Respondents also often noted the downsizing of items like fat-based spreads, frozen pollock, cheese as well as meat products.
"It seems that shrinkflation has specially affected these products, because there were so many similar observations," Pessi explained.
Some food companies claim that consumers have called for the downsizing, while other firms point to rising prices of raw materials, according to the Consumers' Union.
I think it cheats consumers. I will never buy those products again.
However, not all shrinkage is the same, according to Pessi.
"If the price also decreases in proportion to the amount of product being sold, consumers won't lose out," she said, adding that it is always best to keep an eye on weight and volume prices, rather than the per-package cost.
Pessi said that in order to maintain trust with consumers, manufacturers should be up-front about their practices.
You feel a bit misled when they don't mention the size change, and they've even raised the price a little
"When you notice that your favourite product has slowly shrunk in size, you might feel somehow betrayed," she explained.
The Consumers' Union has sent its findings about the survey to the Finnish Competition and Consumer Authority.
The supermarket isn't the only place being affected by shrinkflation, late last year it was reported that Finland's famous "baby box" was also being downsized.