Beside age and sex, the living arrangements are associated with variation of mortality risks for the older adults. Trends in living arrangements of elderly population are associated with steadily improving longevity in the context of population ageing but also with the impact of the second demographic. Recent studies suggest that not only distribution of living arrangements is affected by the mortality improvements but also that different living arrangements have specific association with mortality risks. This raises a question if and how trends in living arrangements of the elderly could be reflected in recent mortality improvement. More precisely, we check how changes in the structure of the older adults by living arrangements could impact the improvement in longevity and if the change observed in the association between specific living arrangements and mortality risks could also impact the change in mortality. To assess the impact of the trends of living arrangements on mortality improvement we use Belgian data from national population register and consider a detailed typology of living arrangements combining the types of co-residence and marital status. Using register data, we had a unique possibility to follow the living arrangements of the population aged 60 years and over from 1991 to 2013. The more important changes in the structure of the population by living arrangements lowering the mortality levels are, for men, the decreasing number of those living with others, living in collective household (being married or widowed) and widowed living alone. For women, the decrease of single living alone is also contributing to the reduction of the number of deaths. At contrary, the living arrangements responsible for increasing the number of death or at least reducing the mortality improvement are, for both men and women, the divorced persons living alone or in collective household and those living with partner.