Corporate members
Corporate members of PI
| ABB Oy | Helsinki | (1972) |
| AEL Oy | Helsinki | (1978) |
| Albany International Oy | Helsinki | (1967) |
| Andritz Oy | Hollola | (1996) |
| BASF Oy | Helsinki | (2004) |
| Christian Berner Oy | Vantaa | (1973) |
| Oy Brynolf Grönmark Ab | Espoo | (1972) |
| Ciba Finland Oy | Raisio | (1974) |
| J. Haarla Oy | Tampere | (1972) |
| Hercules Finland Oy | Helsinki | (1968) |
| Honeywell Oy | Espoo | (1976) |
| Imerys Minerals Oy | Helsinki | (1977) |
| Kemira Oyj | Helsinki | (1970) |
| Kymppi-Eristys Oy | Oulu | (2007) |
| Lyckeby Industrial Oy | Espoo | (1995) |
| Metso Paper Oy | Jyväskylä | (1962) |
| Metso Power Oy | Tampere | (1988) |
| Oy Metsä-Botnia Ab | Espoo | (1973) |
| M-real Oyj | Espoo | (1917) |
| Myllykoski Paper Oy | Anjalankoski | (1952) |
| Nalco Finland Oy | Espoo | (1985) |
| Omya Oy | Helsinki | (1990) |
| Oy POM Technology Ab | Helsinki | (2006) |
| Pöyry Oyj | Vantaa | (1972) |
| Stora Enso Oyj | Helsinki | (1916) |
| Sunila Oy | Sunila | (1996) |
| Sweco Industry Oy | Vantaa | (1974) |
| UPM-Kymmene Oyj | Helsinki | (1987) |
| Voith Paper Oy | Vantaa | (2001) |
| Wetend Technolgies Oy | Savonlinna | (2007) |