Imatinib has transformed the prognosis and the management of chronic myeloid leukemia (CML) and has probably changed the patterns of mortality rates. We explored this change at each disease severity level (Sokal score) through a flexible statistical modeling of the effect of the year of diagnosis on the excess mortality rate. The study included 691 chronic-phase patients from Nord-Pas-de-Calais French CML registry diagnosed from 1990 to 2007. Imatinib was given to 93% of the patients diagnosed after 2000. Comparing the 1990-1994, 1995-1999, and 2000-2007 periods of diagnosis, the 5-year relative survival improved from 64% to 66% and 88%. The year of diagnosis was associated with a significant reduction of the excess mortality, but only in patients with intermediate to high Sokal scores. In high-risk patients diagnosed in the early 1990s, a peak of excess mortality was observed during the second year of follow-up. That peak decreased progressively over the years of diagnosis until disappearing in patients diagnosed after 2000. This study showed different effects according to Sokal scores of the use of imatinib on mortality in patients with chronic-phase CML and showed that since 2000 the pattern of mortality of high-risk patients became similar to that of intermediate-risk ones.