Boskalis sets stock dividend conversion rate at 1:14.5

Papendrecht, 5 June 2009 On 14 May 2009 the dividend of Royal Boskalis Westminster N.V. for 2008 was set at ¤ 1.19 per ordinary share with a choice of stock or cash dividend. With the dividend distribution as stock, shareholders will receive 1 new ordinary share per 14.5 dividend rights of ordinary shares. The conversion rate has been based on the volume weighted average stock price of Boskalis shares traded on NYSE Euronext Amsterdam over the period 3, 4 and 5 June 2009. The value of the stock dividend is virtually the same as the value of the cash dividend based on the 1:14.5 conversion rate and an average share price of ¤ 17.39. Both the cash and stock dividend will be made payable from Wednesday 10 June 2009. Cash distribution will be subject to deduction of dividend tax as required by law. This is an English translation of the Dutch press release. In the event of any disparity between the Dutch original and this translation, the Dutch text will prevail. Royal Boskalis Westminster N.V. is a leading global services provider operating in the dredging, maritime infrastructure and maritime services sectors. Boskalis provides creative and innovative all-round solutions to infrastructural challenges in the maritime, coastal and delta regions of the world including the construction and maintenance of ports and waterways, land reclamation, coastal defense and riverbank protection. The company holds important home market positions in and outside of Europe and targets all market segments in the dredging industry. It also has positions in strategic partnerships in the Middle East (Archirodon) and in offshore services (Lamnalco). Boskalis has a versatile fleet of over 300 units and operates in over 50 countries across five continents. Including its share in partnerships, Boskalis has approximately 10,000 employees. For further information please contact: Martijn L.D. Schuttevâer Director of Investor Relations & Corporate Communications Telephone: +31 78 69 69 822 / +31 6 200 10 232 Telefax: +31 78 69 69 020 E-mail: m.l.schuttevaer@boskalis.nl This press release can also be found on our website www.boskalis.com This announcement was originally distributed by Hugin. The issuer is solely responsible for the content of this announcement.