What this means for learners
Russian and Polish share 20 sounds — roughly 48% of Polish's inventory overlaps with Russian. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 17 sounds found only in Polish represent the greatest pronunciation challenge for Russian speakers. The adult brain tends to map unfamiliar sounds onto the closest native equivalent — a process that produces the characteristic "accent" of a second-language speaker. Learning to hear and produce these sounds as distinct requires focused ear training, not just repetition.
Conversely, Russian has 22 sounds not used in Polish. Native Polish speakers learning Russian will face the mirror-image challenge with these sounds.
Phoneme inventories from PHOIBLE. Data reflects one documented inventory per language; some variation exists across dialects and sources.