The purpose of the study was to compare the effectiveness of programmed and intensified intervention on lifestyle changes, including physical activity, cigarette smoking, alcohol consumption and diet, in patients aged ≥ 65 with the usual care of general practitioners (GP). In this multicenter randomized controlled trial, 738 patients aged ≥ 65 were randomly assigned to receive intensified intervention (N = 371) or usual care (N = 367) of a GP for lifestyle changes, with 18-month follow-up. The main outcome measures were physical activity, smoking, alcohol consumption and diet. The study was conducted in 59 general practices in Croatia between May 2008 and May 2010. The patients' mean age was 72.3 ± 5.2 years. Significant diet correction was achieved after 18-month follow-up in the intervention group, comparing to controls. More patients followed strictly Mediterranean diet and consumed healthy foods more frequently. There was no significant difference between the groups in physical activity, tobacco smoking and alcohol consumption or diet after the intervention. In conclusion, an 18-month intensified GP's intervention had limited effect on lifestyle habits. GP intervention managed to change dietary habits in elderly population, which is encouraging since elderly population is very resistant regarding lifestyle habit changes. Clinical trial registration number. ISRCTN31857696.