There is a recent increase of interest in welfare of lactating sows and piglets in terms of housing system. Several studies have confirmed that the farrowing cages cause suffering of lactating sows, and thus have a negative impact on their welfare. Some countries in Europe have already banned housing of lactating sows in the farrowing crates and some countries are currently in the process of its limitation. In organic farming, rearing of lactating sows in the farrowing cages is not compatible with European Union legislation. It is therefore possible to assume that this issue will be soon addressed also for crated sows at the European Union level. The paper presents an overview of important studies that compare the influence of housing systém (farrowing crates and loose-housing) in lactating sows on their maternal behavior and piglet mortality and focuses on areas that are considered essential to the good welfare of sows and also addresses important factors that affect piglet mortality.