What Not to Bring to Finland
Food
Bringing meat and dairy products into the EU from a non-EU country is restricted, and Finland applies that like every other member state. This is an animal-health rule, not a taste judgement, and it applies to the sandwich in your bag as much as to a parcel of cheese. Arriving from inside the EU, food for your own use is not an issue. If you are flying in from outside the EU, eat it before you land or leave it behind. I am not going to quote allowances here because they change and because customs publishes them properly; check the Finnish customs guidance for your own route.
Alcohol and tobacco
Allowances apply when you arrive from outside the EU, and there are conditions on bringing alcohol in from elsewhere too. Finland taxes alcohol heavily, which is the actual reason this question comes up so often — and it is also why the ferries to Tallinn and Stockholm have the shops they have. If you are sailing, buy on board or at the destination and carry it home within the rules rather than trying to guess. The crossings themselves are covered on where the ferries go.
Knives and weapons
Weapons are restricted, and so is carrying knives in public places. This catches out people who have just bought a puukko, the traditional Finnish knife, as a souvenir — a perfectly normal thing to buy here. Buy it, have it wrapped, and put it in checked baggage rather than a coat pocket. The same applies to multi-tools. The shopping page covers what else comes home well.
Drones
Do not assume you can fly one over the harbours. The South Harbour, West Harbour, Katajanokka and Hernesaari are working commercial ports with international ferry and cruise traffic, and Suomenlinna is a protected heritage site with a permanent population. Airspace rules apply and so do local ones. If you want aerial-looking pictures of the archipelago, the cheaper and more reliable answer is to sit on a sundeck — which is what the sightseeing loop is for.
Things that are simply unnecessary
A voltage converter if you are coming from elsewhere in Europe. Bottled water, because the tap water is excellent everywhere. Formal clothes, because Helsinki does not dress up. Large amounts of cash: cards work everywhere, including on board the ferries. What you should bring instead is a windproof layer, because the wind comes across the open water at Market Square even in June, and a passport or ID card if there is any chance you will cross to Tallinn, because the carriers check identity.
If you are arriving from outside the EU, deal with food before you fly rather than at the customs channel. The queue is unpleasant and the sandwich is not worth it.
Frequently asked questions
Can I bring food into Finland?
From inside the EU, food for your own use is fine. From outside the EU, meat and dairy products are restricted, so check the customs guidance for your route.
Can I bring a Finnish knife home?
Buying a puukko is normal, but carrying knives in public places is restricted. Put it in checked baggage rather than a pocket.
Do I need cash in Finland?
Very little. Cards work everywhere, including on board the ferries, and contactless is the norm.