Developing a solid interest in academic work, he earned his Ph.D. in chemical engineering in 1981, with a thesis on Phosphorus Nitrate Chlorides.
[2] Starting from the period of his research for the Ph.D. thesis and throughout the 1990s, Dan Ioan Popescu authored and published more than 60 papers in speciality journals in Romania and abroad.
Starting with 2009, he gave up all the public functions and re-entered the realm of business, serving as President of Administration Councils and the General Manager of different companies.
The Romanian High Court of Justice (Curtea de Casatie si Justitie) stated that 4.000.000 lei belonging to the Popescu family can not be legally traced, starting the process of confiscating the amount.
In opposition at that time, Dan Ioan Popescu decided to become a member of the Conservative Party and in 2006 he was elected its prime-vice-president.
In the period 2000–2004, as Minister of Economy and Commerce, Dan Ioan Popescu co-chaired a series of intergovernmental commissions for economic cooperation: