This paper deals with two problems, methods of <I>fo</I>F2 trend determination and origin of trends in <I>fo</I>F2, both being controversial in current literature. We found that various regression-based methods and artificial neural network-based method of Yue et al. (2006) provided comparable results within uncertainties caused mainly by various ways of removing/suppressing the dominant solar cycle effect. The role of geomagnetic activity in the observed trends in <I>fo</I>F2 was probably substantial and might be still even rather dominant in the last quarter of the 20th century.