Disclosed herein are anisotropic conductive particles contained in anisotropic conductive adhesive films, which can be used in circuit board mounting applications. The conductive particles can exhibit superior electrical reliability. Further disclosed are polymer particles having good compressive deformability and recoverability from deformation without being ruptured when an adhesive film containing conductive particles including the polymer particles as a component is interposed and compressed between connection substrates, thereby achieving a sufficient contact area between the particles and the connection substrates. Because the polymer particles have a spherical shape, a uniform particle diameter, and a narrow particle diameter distribution, the particles can exhibit enhanced conducting properties.