The aim of the paper is to identify elements of seasonality in supply and demand in the liquid biofuels sector in Poland and Germany. An additional purpose is to present forecasts for selected aggregates until 2020. Two research questions have been formulated for their implementation: (1) is biofuel production in Poland higher in spring or summer (due to the seasonality of agricultural raw material production) than e.g. in winter?; (2) Is the consumption of biofuels seasonal in both countries? The research applies quarterly data for the following aggregates from the biofuels sector: for Poland – production and sale of biofuels in the quarters of 2006-2018, for Germany – biofuel consumption in the quarters of 2007-2017, import and export of bioethanol in the quarters of 2007-2015, import and export of esters in the quarters of 2007-2017. The work focuses on identifying seasonal fluctuations in order to identify purified seasonality indicators, so that it is possible to present forecasts for the biofuels sector. The research conducted in the article leads to the conclusions that, in the liquid biofuels sector, in Poland and Germany, there are elements of seasonality, especially in the field of sales / consumption of biofuels, which in turn is the effect of the changing demand for traditional fuels in which liquid biocomponents are admixed or (less often) used separately as fuel. Differences in the values of variables in Poland and Germany in quarters, in the analysed periods, can be significant – they usually reach several dozen (up to even over 100%), although in nominal terms these differences are usually several or several percentage points. The consumption of biofuels in both countries was higher in the second and third quarters, i.e. in the spring-summer period than others.