New Zealand has lower cancer survival compared to its neighbour Australia. If this were due to long established differences between the two patient populations, it might be expected to be either constant in time, or decreasing, as improving health services deals with inequities. In this study we compared trends in relative cancer survival ratios in New Zealand and Australia between 2000-05 and 2006-10, using data from the New Zealand Cancer Registry and the Australian Institute for Health and Welfare. Over this period, Australia showed significant improvements (6.0% in men, 3.0% in women) in overall 5-year cancer survival, with substantial increases in survival from major cancer sites such as lung, bowel, prostate, and breast cancers. New Zealand had only a 1.8% increase in cancer survival in men and 1.3% in women, with non-significant changes in survival from lung and bowel cancers, although there were increases in survival from prostate and breast cancers. For all cancers combined, and for lung and bowel cancer, the improvements in survival and the greater improvements in Australia were mainly in 1-year survival, suggesting factors related to diagnosis and presentation. For breast cancer, the improvements were similar in each country and seen in survival after the first year. The findings underscore the need to accelerate the efforts to improve early diagnosis and optimum treatment for New Zealand cancer patients to catch up with the progress in Australia.