Three case studies in south-central Chile were selected to investigate the growth behaviour of the Chilean deciduous tree species Raull (Nothofagus nervosa) in mixture with the exotic tree species Douglas fir (Pseudotsuga menziesii). Research sites 1 and 2 contain plantings of different plant associations in pole-stand-Age. Site 3 contains an underwood planting of Douglas fir beneath a 30-year-old Nothofagus pole stand. The height growths of the deciduous and coniferous species in the particular mixture, as well as the question of mutual influence, have been analysed. Site 1 showed a strong superiority in height growth of Raull at the age of 8 years in comparison to Douglas fir. The observations were just the opposite at site 2: The 11-year-old Douglas fir showed predominant height growths compared to the native Nothofagus species. Tree-ring analyses showed that the superiority in height started very soon after planting. At site 3, Douglas fir has reached the crown layer of 60-year old Nothofagus after 30 years. While a mixture of trees of the same age appears to be possible in the temperate climate of the province of Valdivia, it might not be successful in the Mediterranean climate due to the strong growth superiority of Douglas fir. However, a positive effect on the growth can be achieved with the underwood planting of Douglas fir beneath a strongly thinned pole timber stand of the native Nothofagus species.