Paper addresses the recent initiatives of EU Lisbon Agenda to increase level of R&D expenses in EU Member States by studying firm-level panel data in most advanced transition economy, Slovenia. Previous empirical literature mainly cross-sectional has tested the demand-pull hypothesis and found in overall that R&D expenses may be driven by output. Using a panel of over 150 Slovene firms over the 1996-2000 period, and checking for fixed effects, time, industrial and size dummies and for the path-dependent nature of R&D, we also find a significant role of sales in inducing R&D expenditures. Besides that data also confirm that internal funds and (un)successful bargaining for higher wages present significant variables for higher R&D expenses. However, at the micro level, the demand-pull, internal funds and bargaining effects play a varying role for the different sub-samples of firms. In particular, exporting firms, those which are liquidity-constrained, those not receiving public subsidies and those not heading a business group, seem to be particularly sensitive in deciding their R&D expenditures. R&D behavior at the firm level is modeled as error-correction model and estimated in system GMM specification.