Abstract: The present invention provides a process for producing paper or board, comprising slushing a stock of dried fibres in a slushing system comprising a pulper, and/or feeding a stock of never-dried fibres in a fiber line of an integrated paper mill; deflaking and/or refining the stock in a deflaker and/or a refiner, optionally diluting the deflaked and/or refined stock, directing the deflaked and/or refined stock to a headbox, forming a web, and drying the web, wherein a polymeric paper making additive is added to one or more of the stocks of dried fibres and never-dried fibres before deflaking and/or refining of the stock. The present invention further provides paper and board with improved properties.