A dry powder formulation for use in a dry powder inhaler comprising: a) a fraction of fine particles made of a mixture composed of 90 to 99.5 percent by weight of particles of alpha-lactose monohydrate and 0.5 to 10 percent by weight of magnesium stearate, said mixture having a mass median diameter lower than 20 micron; b) a fraction of coarse particles constituted of alpha-lactose monohydrate having a mass median diameter equal to or higher than 100 micron, wherein the ratio between the fine particles and the coarse particles is between 1:99 and 30:70 percent by weight; and c) formoterol fumarate dihydrate in combination with beclometasone dipropionate as active ingredient both in form of micronized particles; wherein i) no more than 10% of said BDP particles have a volume diameter lower than 0.6 micron and the d(v,0.1) is comprised between 0.8 and 1.0 micron, ii) no more than 50% of said particles have a volume diameter comprised between 1.5 micron and 2.0 micron and the d(v,0.5) is comprised between 1.5 and 2.0 micron, and iii) at least 90% of said particles have a volume diameter lower than 4.7 micron and the d(v,0.9) is comprised between 3.0 and 4.0 micron; wherein said BDP particles are further characterized by a particle size span, defined as [d(v,0.9) - d(v,0.1)]/d(v,0.5), comprised between 1.2 and 2.2; whereby said volume diameter is determined by laser diffraction using a Malvern apparatus; and whereby said formulation is therapeutically equivalent to a corresponding formulation for pressurized metered dose inhalers (pMDIs) containing the above active ingredients dissolved in a mixture of ethanol as a co-solvent and HFA134a propellant. a) a fraction of fine particles made of a mixture composed of 90 to 99.5 percent by weight of particles of alpha-lactose monohydrate and 0.5 to 10 percent by weight of magnesium stearate, said mixture having a mass median diameter lower than 20 micron; b) a fraction of coarse particles constituted of alpha-lactose monohydrate having a mass median diameter equal to or higher than 100 micron, wherein the ratio between the fine particles and the coarse particles is between 1:99 and 30:70 percent by weight; and c) formoterol fumarate dihydrate in combination with beclometasone dipropionate as active ingredient both in form of micronized particles; wherein i) no more than 10% of said BDP particles have a volume diameter lower than 0.6 micron and the d(v,0.1) is comprised between 0.8 and 1.0 micron, ii) no more than 50% of said particles have a volume diameter comprised between 1.5 micron and 2.0 micron and the d(v,0.5) is comprised between 1.5 and 2.0 micron, and iii) at least 90% of said particles have a volume diameter lower than 4.7 micron and the d(v,0.9) is comprised between 3.0 and 4.0 micron; wherein said BDP particles are further characterized by a particle size span, defined as [d(v,0.9) - d(v,0.1)]/d(v,0.5), comprised between 1.2 and 2.2; whereby said volume diameter is determined by laser diffraction using a Malvern apparatus; and whereby said formulation is therapeutically equivalent to a corresponding formulation for pressurized metered dose inhalers (pMDIs) containing the above active ingredients dissolved in a mixture of ethanol as a co-solvent and HFA134a propellant.