Study was focused on effect of silicon (Si) on growth and nutritional status of sunflower ( Helianthus annuus L.) under low boron (B) external supply. Plants were grown under controlled environmental conditions in nutrient solutions with two low B treatments (0.2 μM B and 0.5 μM B) with or without addition of Si and control treatment containing sufficient B supply. Shoots growth was only slightly affected by Si supply while accumulation of B in fully developed leaves was significantly higher only at 0.5 μM B. In roots nutrients contents were relatively constant while accumulation of all nutrients in leaves was affected by addition of Si. Differences were significant only in K Fe and Mo between treatments 0.5 μM B and 0.5 μM B with Si added and in Zn between both treatments. In comparison with other studies results confirmed that plant species show different response to Si application. Interaction of B and Si should be involved in further research in B deficiency in sunflower.