leaving Poland on Canadian passport

I routinely fly between the Schengen area and a non Schengen country using a passport from an EU country and one from the non-Schengen country. You should be able to do the same flying between Poland and Canada, using your Polish national ID card. This is how:

1. Check in for your flight to Canada with your Canadian passport.

2. On your way to the departure gate, you will go through a government-operated passport checkpoint. Show your Polish national ID card here.

3. For the rest of the trip, show only your Canadian passport.

This assumes a direct flight between the two countries. If the flight is not direct, follow this rule: show the Polish national ID card to any government official of an EU or Schengen area country; show the Canadian passport to everyone else.

You can certainly leave the Schengen area through Italy; in that case you still normally not encounter any Polish government officials. But if you show your Canadian passport there, the Italian border officer should look for stamps to check whether you've overstayed in the Schengen area. Instead, you should show your Polish national ID card.

It's important to note that the purpose of this document switching is not deception. You aren't hiding anything. You are simply showing the document that establishes your rights as an EU citizen to EU officers and the document that establishes your rights as a Canadian citizen to Canadian officers and to the airline. If any questions ever arise, it's perfectly acceptable to show the other document to anyone.

Trying to board a direct flight from Poland to Canada:

1. Your Canadian passport can be rejected on the grounds that Poland doesn't allow exercising other citizenships for Poles.
2. Your Polish ID will undoubtedly be rejected on the grounds that it's not a valid document for out-of-EU travel.

#1 is informally known as "Polish passport trap". Enforcement of this policy comes and goes, but legally it's valid.

You can use your ID to leave Poland for another Schengen country (like Italy). Once you're outside Poland, rule #1 no longer applies are you can use your Canadian passport to leave Italy. That's airtight as long as your Canadian passport is still valid.

You can get a new Polish passport, leave Poland on it and enter Canada on your old Canadian one. That's also airtight, no matter how old the Canadian one is.

You can push your luck by pretending you're not a Pole at all and try to board plane in Poland using Canadian passport. That might work, as long as your Canadian passport is valid and nobody would notice or care you're also a Pole. But it's not really legit and I don't recommend taking this route if you can take one of the others.

As an EU citizen, you cannot overstay in EU or Schengen area and must be allowed entry.

As a Canadian citizen, you cannot be denied entry to Canada and you cannot lose your Canadian citizenship without voluntarily renouncing it (other than if you obtained Canadian citizenship by fraud or misrepresentation), even if you obtain or get another nationality recognized .

If you have a valid Polish identity card that establishes your EU (Polish) nationality, it is a valid travel document in any EEA country and Switzerland and it is a Polish document recognized by Polish border guards.

From Polish Border Guards' website, regarding dual citizens:

W związku z pojawiającymi się w ostatnim czasie wątpliwościami, co do zasad dokonywania odprawy granicznej przy przekraczaniu polskiej granicy państwowej przez obywateli RP z podwójnym obywatelstwem, uprzejmie informujemy, że wymóg okazania funkcjonariuszom Straży Granicznej podczas kontroli granicznej polskiego dokumentu paszportowego lub odpowiednio dowodu osobistego dotyczy wszystkich obywateli polskich.

With regard to recent doubts concerning the rules for border checks carried out when crossing the Polish border by citizens of the Republic of Poland who are dual citizens, we would like to inform you that the requirement to present a Polish passport or, respectively, an ID card to the Border Guard officers during border control applies to all Polish citizens. (Translated by DeepL)

It also allows you to pass the exit check of the Schengen Area or another EU country. So you can travel to Italy or France, and you can pass the exit check when you leave Italy (or another EU country) for Canada without problem.

When you enter any EU country again from anywhere, your Polish ID alone also suffices.

You will need your Canadian passport and present it to the airlines when you are travelling to Canada (and most countries which do not accept Polish ID as a valid travel document).