The man, who was in his 60s according to the officials, was traveling by train from Moscow to Nice when his luggage was checked by Polish guards at the railway station in Terespol, close to Belarus.
The size of the man's suitcase drew the attention of the officers, border guard spokesman Dariusz Sienicki said AFP news agency Monday.
"To their surprise, a woman in her 30s emerged. It was the Russian wife of the owner of the suitcase," he told AFP.
"She was alive and well and didn't require medical attention."
Risking three years in jail
There was no need for hiding, however, because even people without European Union citizenship are allowed to enter the passport-free Schengen zone if they can prove they are married to an EU citizen.
"Had she been sitting next to her husband, she would have made it through without incident," Sienicki said.
Instead, the couple had risked "a three-year jail sentence because of their attempt to evade border control," he added.
"This was the first time I've seen someone travel like this. She very well could have been a victim of human trafficking."
The couple was released after questioning and decided to go back to Belarus.
dj/kms (AFP, Interfax)